I own multiple climbing shoes, but these are the ones I always repurchase. They're a great for bouldering and sport climbing. I've jammed these into a few cracks, and while I wouldn't recommend using them for that, the worked passably. I wear a women's 7.5 (sometimes 8) street shoe and I bought a size 38 (size women's 7). I cried for the first couple of climbs, but they stretched out to a tolerable fit. If you're looking for a more comfortable fit I suggest you get your regular shoe size.

The Scarpa Boostic is a superlative technical edging shoe. Besides edging on tiny credit cards, nubbins, and crystals and toeing into pockets, it also shines in other, unexpected areas. Due to its moderate downturn and high stiffness, the Boostic allows you to pull in with your feet like hands. If sized snugly, you can edge on anything. (For a wide foot like mine, this is .5 size above street shoe size) When sized more generously, it is also a surprisingly sensitive shoe for smearing and smedging, a decent granite crack shoe, and a comfortable all-day performance shoe, all while preserving most of its ridiculous edging power. (Full size above street shoe for me)
Due to the absurd amount of power in the toe, this shoe always feel sticky, even with Vibram Edge rubber.
Narrower feet will still fit well but a smaller relative size will be required.
For any angle of edgy or pockety limestone, nothing that fits my foot compares. You can go virtually hands free on small edges due to the stiffness and support of the shoe. This is the ultimate shoe for technical granite climbing as well. Size snugly for single pitches and size more generously for long, hard free routes. Unlike most new performance shoes, this shoe achieves its phenomenal edging power not only from the tension between the big toe and the heel, but also from its sheer stiffness. This allows it to preserve impressive edging performance even when sized for comfort.
I only have two complaints about this shoe:
The first is that the heel is baggy when the rest of the shoe fits. This is more due to my small, narrow heels than a fault of the shoe. The second complaint is that the shoe is fairly high volume, so if you size up, expect to cinch the straps all the way down.
I really hope Scarpa doesn't discontinue or "improve" this shoe, as that would be a huge disservice to the climbing community. Just look what shoes Peter Croft and Josh Wharton wear for most of their climbing...

Looking to crush some hard routes? BUY THESE.
If you have "Scarpa foot" (wide forefoot, high-volume foot and heel), chances are this shoe will fit great on you. I wear a size 9/42 in my street shoe and I got these in a 41.5, and its a great performance fit without extreme discomfort. Break-in period is a little painful, but after a few long climbing sessions they'll stretch to your foot/your foot will mold into them.
They perform fantastically on just about everything besides slabs or cracks, but they really shine on vertical-to-slightly-overhanging routes. They have incredible edging power on all types of rock, and do very well steeper terrain as well. For truly overhanging roof climbs, I would wear something with a softer, stickier rubber. Heel and toe hooks are great, very secure without any slipping or pain.
Buy these shoes fairly tight, and throw them on to send your hardest routes. Or buy them in a more comfortable size, and you could probably use them on just about everything. Scarpa makes some of the best shoes on the market, and you can't go wrong with these!

These are really comfortable for an aggressive down-turned shoe. Performance is solid.

I am size 9 street shoe. I wear these in a 40.5. I wear the Instincts in a 40, for comparison. In La Sportiva Katana, I'm a 38.5.

I purchased these for a friend, but here's his feedback: "The Boostic is the climbing shoe of ultimate sending destiny. This shoe fits a narrow foot well and it fits true to street shoe size. I wear a size 10 street shoe and the 42.5 (9.5 Mens US) fits snug and perfect. They seem to wear pretty well so far, it’s been about 8 days in the gym and on sandstone without much noticeable wear. But man, did these bad boys step up my climbing game. They can hold an edge on the nipple of a polished marble statue covered in Vaseline like nobody’s business. I can climb stairs made for ants! I can stand on a nail head! IT’S LIKE I HAVE FRIGGIN TREEFROG HANDS FOR TOES!!!!!!!!! I like them."

I bought this shoe in November 2013, and has been on rotation as my go-to shoe for all of the steep and/or thin routes and boulders or anything where I feel like I could use the extra confidence in edging. The break-in period was painful (I bought a size EUR 45 - I wear a US 12 street shoe) but only a month or so long (2-3 climbing days per week, shoe off IMMEDIATELY following the climb). After the break-in, the shoe feels locked-in without excess pressure points.



Two-and-a-half years and two resoles (Rock N Resole in Boulder, CO) later, my feet still turn blue. All of the edging performance you'd ever need, and all it costs is very festive feet for the rest of the life of the shoe. Endless reservoirs of blue and green leather dye. It's almost as impressive as the performance of the shoe.

These are my first pair of Scarpas and I am very pleased with how comfortable they are! My first pair of aggressive shoes were the La Sportiva Miuras, and though they climbed extremely well, my feet were always in pain. My feet were just a little too wide to ever be comfortable in the Miura so I decided to switch to the Boostic. I went up a full size from my Miuras (though I could have crammed into a half size) because I wanted something a little more comfortable. The Boostics are very stiff and have performed very well in the gym and on the limestone outside of St. George last weekend! All in all my favorite qualities of this shoe are: Sticky rubber, aggressive downturn, secure closure system, and very excellent toe, heel, and edge performance! Grab a pair today!

I have wide feet so I am pretty picky about what shoes i cram them into. The Evolv Shaman were a good fit (I ran them in my street shoe size-10) and now I got the Boostics in a 42.5 and they fit great. The breakin period was a bit rough but didn't take too long til they confirmed to my foot. But them tight and tough it out. First time using these in the gym I crushed some problems I had been projecting. Worth the money in my opinion

This is a nice shoe to use for both bouldering and sport climbing. It is pretty sensitive and precise yes supportive enough. Nice fit and high quality materials from scarpa. The leather breaks in awsomely.

Amazing shoe. I got a bunch of difference shoes to test out, and i used this one after the five ten anasazi on a small overhang artificial boulder. Wow! i went up much faster and my feet were so much more precise and secure with toe locks, heel hooks etc! Then i realized it was the shoe, not me, and i came back down to earth :)



Now, the ever difficult question, sizing!

This shoe runs smaller for me than other Scarpa. I am a street size 6-6.5 women; 36-36.5 european and i bought a 37 in the boostic. They are very snug on, and i would not say standing in them is comfortable. They feel good climbing though. These would compare to a 36.5 in vapor v or instinct.



I have sportiva women solutions in 36; miuras in 35.5 for further reference



Photo, coming out from the overhang, i have the left toe jammed in, the right heel hooked on the side, i was so secure on the feet i basically stood up next...! love these shoes

Street shoe: 12
Wide Foot
Size in the Boostic: 45/11.5
Uses: Sport Climbing, Bouldering
Tested: Sandstone and Limbstone

What to say about this shoe? This Shoe is a Crusher of Stone! I love everything about this shoe. I have a very wide foot with a high arch, it was always a pain to find a shoe that had performance fit but didn't kill me. I like to wear my shoes at a comfortable tight! I have this pair in a 44 for Bouldering and 45 for Sport Climbing. The way Scarpa designed the shoe is Amazing, Powerful but comfortable. Scarpa did a mixture of Suede and Loirca: Suede will stretch and Lorica will not. What this does is allows the shoe to stretch where you need it and keep the last of the shoe. Be prepared for a break in period!

Pros:
-Crusher Of Stone!
-Powerful
-Heel Hooks
-Comfortable
-Edging Guru

Cons:
-Price!

I've never owned a pair of climbing shoes before that were actually sized according to the street shoe size, but these are right on the money. I wear a women's 7.5 and I bought the 38.5. They were exceptionally painful to break in, but after a few sessions in the gym they were ready to take to the crag with very little, to no pain.

I have been climbing in these shoes for 8 months and just wore a hole in the toe. These are my gym and outdoor shoes, I have been consistently climbing in these 5 days a week for 1-1.5 hrs per session. They are great for steep and technical edging. LOVE the suction these shoes have from the moment you step into them. I wear a 9.5 street shoe and bought these in a 42.5. They were a little tight on the break in period but now are very comfortable. I have a smaller heel so there is a little bit of space right there. I have never had a problem heel hooking anything in these though.

I am able to place my feet on anything and feel confident doing so with these. These are my go to shoe. I love when I first put them on and they suction to my foot and I am ready to send.



Shamans in size 10 ~ 43

Boostics in a 42.5

These are the most comfortable climbing shoes I've ever worn. Never have I felt more comfortable on my toes.



I've got a bit of a wide foot and had tried to find a pair of La Sportivas that fit well, but never could. Before the Boostics I wore the Instincts and loved them. After the soles wore out I picked these up and couldn't be happier. I highly recommend them.

If I had to describe these shoes I'd say they are the Ferrarri of climbing shoes. Although they aren't the best for smearing on steep angle slab routes, they more than make up for that in everything else. They're my go to for any steep, overhung or thin, highly technical face routes. I wouldn't be afraid to say that these bad boys may even help you send higher grades then you thought were possible. I love them so much I ended up picking up a second pair for gym use. A must for anyone who wants to climb hard!

Very stiff shoe compared to most of the rest of the Scarpa line. Shines in bouldering, but seemed to me to be more suited to vertical or moderately overhanging routes. The stiff edge combined with a gentle downturn is potent when you need to take a lot of weight on small feet while still pulling into the wall. I first tested these shoes on a vertical route near my house revolves around a tenuous cross with microedge feet. Normally I do this move dynamically, so I was shocked when I could stand there virtually hands free in a fresh pair of the Boostiks.

Seems to run a little (1/4 size?) small.

The Boostic is my top choice for demanding technical edging on slightly-less-than vertical to slightly overhanging terrain. It is stiff and holds tiny edges like a champ but doesn't feel like wearing clogs, nor does it feel like its rolling off of edges, as softer-rubbered shoes can. This inspires great trust and helps avoid the dreaded foot popping that can happen when trying to put just the right amount of weight into a teeny-tiny foot edge. I feel like these run a bit tighter than other Scarpa climbing shoes.

Awesome downturn, incredibly sticky rubber, fit true to size. I wear Scarpa Vapors and they both fit perfectly in soze 42, I wear a size 9 street shoes. My feet tend to be a little wider at the toes, so I wasn't able to wear the five ten anasazi or sportiva solutions as they pinched in on my feet. I predominantly use these for bouldering, but could easily see myself using them for sport. They're aggressive, stick, and slide on like a sock with great rubber for toe and heel hooking.