I have the Gamma SV, which I believe is uses a slightly heavier version of Poweshield fabric. It does remarkably well in constant snow. I was skiing last year at Loveland in it (the jacket was pretty new) and was amazed at how well it shed snow and how dry I stayed. It never wet out at all. That being said, I still trust my Goretex XCR (also Arcteryx) jacket more if the conditions are going to be awful, in part because it has a hood, but in part because I have lots of years of experience with goretex and limited experience with soft shells.
I also don't know how much of the snow repellency is due to the fabric itself and how much is due to the DWR coating. Will it do as well when it is older? I suspect from looking at the weave of the fabric that much is due to the fabric itself, but perhaps someone with more experience can answer that.