As the other reviewer mentioned, these are great for backpacking, and are an ideal choice for warm weather, especially in the microweight thickness. They soak up sweat well, and you benefit from evaporative cooling. These are extremely soft against the skin, as are all of SmartWool's products. I like the cut and fit as well; fitted, but not skintight, and definitely not baggy.
I don't wear wool all the time, as I find myself drawn to plastics, recycled plastics, more and more. Sometimes, however, wool just feels right, and SmartWool does wool right, whether it's shirts, socks, beanies, or baselayers.
If I have one gripe, it is the tag, which sits about 3-4 inches up from the hem on the side seam of the shirt. It is just high enough to be against my side, and not against my shorts. Sometimes I notice it, sometimes I don't, but when I do, it bugs. I have even turned my shirt inside out on a hike to avoid it. I have no desire to take scissors or a blade to my new $65 shirt to cut it off.
For this kinda dough, I expect these shirts to be perfect. So many companies have gone tagless; I beg you, SmartWool, do the same. I am still giving this shirt five stars, but until they go tagless, "Almost Perfect."