Raymond G.wrote a review of Arc'teryx Proton AR Hooded Insulated Jacket Men's on January 12, 2017
Familiarity: I've used it several times
Fit: Runs small
I just used this out snowboarding for a week in -7C (roughly 19.4 degrees) daytime average with winds anywhere from about 5 - 22 miles per hour. I used it under an Acteryx Sidewinder SV alternating with Arcteryx LTW and Arcteryx Phase AR shirt Baselayers.
I had high hopes for this for use under a gore tex shell snowboarding in very cold conditions. It was mostly on piste with some off piste and chair lifts.
It worked very well at keeping me warm, and breathed very well and not sweaty at all or too hot, on the contrary on the the lifts approaching 1/3 from the top my wrists and forearms felt slightly cool. So it warms up nicely when active, but breaths and lets excess heat and moisture out.
I'd say it's pretty darn good, but with many Arcteryx products I'm always disappointed with the lack of pockets. I talked to one shop staff at Arcteryx who is from the Alps he said we in Europe don't care so much if they save 5 grams of weight, pockets are something you rely on.
The two chest pockets are great (and a surprise), looks like a Norrona copy for the chest pockets, but as a mid-layer specific jacket it needs at least one interior mesh pocket to defog goggles or warm gloves and it also needs a pocket for a music player. Both are a must have. What do you do when you need to defog goggles on mountain, put them under your shell and hope they don't fall out?
Sizing, I'm 5'9", 32" waist, as others have stated the arm pit area is a bit snug and could certainly be opened up. Waist fits just barely and frankly could be looser by an inch or so and could be longer by and inch or so.
I already owned the Acteryx Nuclei AR and I was closely comparing both during my week snowboarding. In very cold conditions I preferred the Nuclei AR hands down over the Proton AR. It's longer, looser, breaths nearly the same and is warmer in very cold conditions, not significantly warmer, but I'd say 10-15% which is just enough, has an interior mesh pocket, and a large helmet compatible hood - I love large hoods, but needs a music device pocket and chest pocket. Even though the Nuclei AR is a larger jacket, it just slides effortlessly under a shell the interior lining I believe is one of my all time favorites of any jacket I own, it's silky soft and slides over any layer.
I gave the Proton AR 3 stars due to the lack of interior pockets and snug fit. Fix these issues and it's a 5 star jacket.