This thing does exactly what it's supposed to... I just wore it every day on a 5 day backpacking trip and it kept me dry on the way up, and warm on the way down and at night. Its comfortable and the zip top is key for releasing heat on a tough climb. At night or on the slopes it's great as a base layer. Can't say enough about this thing... After 5 days in the wilderness, I come home and my wife says it smells clean. Pretty amazing!

Perfect weight for fall temps. (40s-50s). Under a wind shell a great combination for hiking, maybe a little warm for running. Icebreaker merino is super soft. Doesn't hold odor. Wicks well and dries fast and doesn't feel clammy even when drenched in sweat. Cut is very athletic, as in skin tight, so if you like something looser, go with Smart Wool. It's stretchy though, so not uncomfortably tight. I just wouldn't wear it around town. A little too revealing for that. Slim is good work working out though. The collar height is nice, not so high that the zipper rubs under the chin. I like the raglan sleeves too (i.e. no seams, flat or not, on shoulders to chafe under pack straps). The zip could be maybe and inch or two deeper for more venting.

I have used this top twice while backpacking. The first time was a day hike in about 60-65F weather. The breeze cut thorugh it and kept me just the right temp. When I stopped my back was a little wet from the backpack and sweating, but I was very comfortable while lounging and enjoying the scenery. The second trip it was 40-50F. This time I had a full 50 lb pack for a quick overnighter. While hiking it was perfect. The zip allowed me to control my temp and I never overheated, but felt comfortable. When making camp I was fine and when the wind kicked up added a MH Power Stretch and hat. I couldn't believe I was still warm. I needed nothing else. I am 6', 170#, 33 in waist, and the large is perfect. I have worn it in public on the way to hiking and was at first a little self conscious, but as I get older I don't give a rat's A$$ anymore. My wife says it just shows that I am fit and will even be seen with me, so it must be fine. I also bought a 260 and assorted leggings based on my great experience with the 200. It hasn't been cold enough to wear them out, although I did wear the lightweight leggings for PJs and I was very warm. I'm sold on icebreaker.