Under Armour is awesome stuff, I have used the cold gear for several seasons. The only problem that I have found is when worn for long durations in the back country, it tends to get a funny odor, kind of a rubbery sweaty smell.

I know that you did not want a debate on scent lock, but if you plan on going for several days without creature comforts, Medalist makes awesome base layers with silvermax and skinetics technology. They not only help with scent control to the animal, but greatly enhance the wearability for longer periods of time. the later of which is why I started using Medalist gear.....