I won't argue the superiority of wool under very cold conditions...but with temps that have already dipped into the 20's in N.GA, I've been very comfortable in my Sitka gear, and I get cold easily. I've tried a truckload of clothing and never once thought any "system" could compete with my hard earned knowledge that dictated my very selective choice of each individual piece of clothing. I was wrong.
I often walk 1/2 a mile or more to my stands and even in cold (for me) temps I work up a sweat carrying the clothes I'll need to stay there and the other gear I may need. I have yet to find anything that wicks like the core zip top...for once, whatever sweat touching it is gone, even in our humid environment. The traverse shirt is amazingly warm for how thin it is and the celsius vest is the same very high warmth to weight ratio.
Coupled with a down vest and fleece jacket, I'm snug and comfortable as long as I want to sit. Mainly, for the first time ever, I can shoot without any restriction because of the ultra thin and highly flexible materials. I'll let you know how the celsius bib and jacket do when mine get here (I needed to order up a size with layering and my middle-aged middle).
By the way, I liked the gear so much, I pursued trying to get on their pro-staff, which I now am. After putting it through the wringer, I am a rabid supporter simply because it was a remarkable improvement from what I had before.
For those who spoke of poor quality issues, I would sincerely appreciate an email with details to pass along to the Q/C team. I'm not sure how the product could get much better but there's always room for improvement.
My apologies for thread hi-jacking, I simply responded because I have yet to see, or hear of any issues with the quality or performance of Sitka gear and I really think it's a superb option in any hunter's arsenal. As Alan said, ymmv.