Ito Jakuchu wrote a review of Arc'teryx Atom SV Hooded Insulated Jacket - Men's on April 6, 2014
Familiarity: I've used it several times
Fit: True to size
I had a fleece that I had to return due to excessive pilling and to their credit Arc'teryx offered to replace the fleece with another item of my choice. I hadn't expected this (as I thought they would just send me a replacement fleece) but I'm extremely happy they send me the Atom SV .
I can't imagine using this as a mid layer, but as an outer jacket it is fantastic. The fit is great with superb cuffs, dropped hem, and an incredibly comfortable hood. The hood adjustments really make this thing bomber when it gets seriously cold or when there is a high wind chill factor.
I am 184cm, 72Kg (6.1/160) and the Medium fits me great. The Atom SV is sized so that you can layer it over some mid layers, which for me at this size it does great. I bought a Medium Atom LT because I liked the SV so much and it fits perfectly under it. A thick fleece or thin down sweater will also easily work. If you want to layer over a thicker down jacket you might want to get a bigger size in order not to compress the thicker down baffles as much.
If you need a synthetic insulator piece with a super comfortable hood, great cuffs and overall fit, this piece is absolutely fantastic and you can't go wrong with it.