Yeah, underarmor, and the similar stuff, is awesome. It's light weight, not bulky and really warm. Took my son camping a few weeks ago in Dover (with the cub scouts) it got down to the high thirties at night and we slept in a tent. I wound up sleeping in a sleeping bag with basically just the base layer stuff on and was quite toasty warm in there.
i wore them out this weekend and they delivered. played some hockey on saturday and football on sunday. sunday was below freezing with 20 mph winds and it didnt phase me. gotta make sure to get the ones with a slot for your wiener though. y'never know