I generally wear ski and mountaineering shells and fleece, but only because I was in in the industry of a lot of years, accumulated a lot of this type of clothing, and am pretty comfortable in it. I also don't like wearing tight clothing. I can't say I've suffered because of it. A lot of cold-weather climbing layers have long tails (not as long as bike specific stuff) and arms to avoid baring the midriff and wrists when reaching above one's head. The few bike specific things I have, I bought for the the reflective qualities, or because it was a deal I couldn't pass up.

It also seems to me that mountaineering clothing provides a lot more ventilation options, which is good for me as my biggest problem is usually overheating.

Just saying I wouldn't rule something out just because it isn't made by [[ insert bike company here ]] if it fits and is a good deal.