I'm a climber and I live by the tube-style belay device. A friend introduced me to the Pirana for Canyoneering and there is absolutely no way I would ever go back to a tube for canyons. No matter what rope we're using, from super stiff, static 8mm to totally dynamic 11mm, single or double strand, I have tons of options for friction - low friction for dry descents, add a little when things are wet, lock off during the descent with a quick flick of the wrist (quick mule-knot if I'm going to sit / do something for a while), etc. So many options, so easy to use...

I tried two pairs of these shoes (44 & 45, I normally wear 44). Both times, I stuck to the canyons like no one else. Amazing traction. Great venting so my feet dried quickly. But dang, my feet HURT in these shoes and I don't have thaaat wide feet! These shoes are really narrow. So I agree with everything the other reviewers said, and now I'm hoping LaSportiva comes out with wider versions!

I love my tiblocs. I generally prefer not to carry extra equipment on me, so after trying various ascenders (for canyoneering, so I'm not doing huge ascents), my preference was various cord ascenders (bachman/prusik/valdotain/french braid)... until I encountered a particularly difficult 200 ft ascent, and now I'm 100% happy using the tiblocs. They go over edges very nicely and add no weight to your harness. Caveat - use a small accessory cord so you don't drop the tibloc, since you have to take it off your biner to clip it to the rope. AND, make sure the biner is set in place before you weight the tibloc EACH TIME you move it - or you'll have a messed up hairy rope!

I purchased the Retros right before going to Mt. Whitney and doing the Mountaineer's Route. The Retros were great up the scree, the scrambling, etc. We detoured to a class 3/4 final climb to the summit. We also bagged Keeler and Day and then grabbed Mount Muir, too, all as a one day. On Mt. Muir, my partners were feeling pretty sketch in their boots and trail runners, but I stuck like I was wearing climbing shoes.
The downside, however, was when we decided to hike the "tourist" route out. After a pretty tough half-day climbing up, 11 miles of rocky trail is quite long and trudging, especially with the lack of any forefoot padding in the Retros. My 1st metatarsal on each foot was pretty sore by the time we got back to the car.
Perfect shoe up till about mile 15 in total, after that, I wanted at least a trail runner's padding, or maybe a runner's silicone metatarsal pad?