I personally love compression gear. I hated it at first, but once I got used to it, I completely forgot that I'm wearing it.
UA is not shit. It flat out works. Now whether or not they are overpriced is debatable. I get tons of UA gear because I get discounts on them, but some other good brands are Patagonia, SmartWool (yay for merino wool!), and Helly Hansen.
As for compression gear riding up... non-issue for me. I can see it doing that if you get the wrong size though. I find loose fitting clothing rides and bunches up way more. Also, I noticed that compression gear makes me feel better after wearing them. Less soreness. So couple that with good rounds of stretching before and after sessions is awesome. As people have said, the compression absolutely wicks moisture better. That's another huge plus.
For my upcoming tahoe trip, I am going to wear compression cold gear for my first layer and a merino wool mid-layer with my very lightly insulated (60g) jacket. If you wear shells, you could do three layers underneath for colder conditions.
I got the correct size, fuck you for even suggesting I didn't. I have a few compression shirts from UA that I wear for running, they ride up while snowboarding. It's because of the lousy slippery material. If you get their winter thermals you won't have this problem but with their general compression shirts you do, guaranteed. Same goes with NikePro as they use the same slippery material.
UA is also not overpriced, in fact it's quite cheap, cheaply made, cheap on the shelf. Also the benefits one would gain from a compression shirt versus a regular base layer is so minute that you are unlikely to see better performance results unless you are a top athlete. People sure do get suckered in "oh it holds my awesome muscles in place so I can preform better and look cool" It makes such a minuscule difference in your bodies performance you can just discount it entirely.
If you've ever spent some time hiking, mountain climbing, or backcountry snowboarding you know it's good to invest in some quality base layers. IMHO Arc Teryx makes the best.