I have an older Polartec version of this jacket and it's been one of my absolute favorites. The Gamma AR has been comfortable and warm from the Cascades (with adequate layering) to hanging out in downtown Seattle or Portland. Sheds light rain, cuts the wind, and breaths well during more active pursuits. No complaints whatsoever.
I just picked up the new version with Fortius 3.0 and wrote a review that wasn't entirely fair. So, I'm rewriting it a bit. This new jacket is almost identical in design to the old one. The fabric is stretchy, hangs a little lower in the front than the old style (which is nice), lightweight, good pocket placement, nice range of motion, and that great Arcteryx style. When the temperature falls much below 30 degrees, the new Fortius face fabric expects you to be active to provide real warmth as a standalone shell. The original jacket, with Polartec, immediately felt warmer. This is still a great jacket. After hiking or climbing with it, it makes a great mid layer under a shell. So far, I like the Polartec version a little better but I would still buy this one again. Oh, I haven't had any issues loosing things out of my pockets. Arcteryxs brilliant designers put zippers on mine to keep them closed. I know! Innovative, yeah? New Fortius 3.0 AND zippers on the pockets! 5'8, 170 pounds, size medium, fits perfectly with enough room to layer underneath.