First off, this top is very flattering . The photos don't do it justice. It's pieced together to enhance and show of your natural curves. So, it's crucial that you have this on if you need to impress someone, at the top of the skin track. Just don't let them take a photo of you while you're in the middle of eating.. ;)
But more important than the aesthetics, this design gives you a full range of movement, without displacing the shirt. It has a good length too, so you don't have to worry about it riding up and exposing skin.
This mapping on this is extremely well-thought-out, for both warmth and breathability. It's not my thickest base layer, but it's the one I want to get sweaty in. This will be your first choice for hard hikes, cold runs, and every ski tour. It breathes really well, while providing some warmth and protection from the elements.
Make sure you wear this next to skin. I wore a base layer under it, on a colder day. But, that just prevented the shirt from working properly and I just got soaked. So, keep this one next to body, so you don't soak up your clothes with sweat, and catch a chill.
I have between using this for ski touring and hiking, but also in the resort. It's easy to work up a sweat in the restort, and the last thing you want is to be sweaty on the chair lift. So basically, I've been living in this base layer, this season. It's doesn't easily stink up, which is a HUGE PLUS!
The fit is perfect for me and really comfortable. I'm typically a medium and got a medium in this. Base layers are often a little too tight and short and in the waist, for me. But, this is spot on, in the medium size. I'm 5'8, 135lbs.