I have been a big fan and user of Merino for a number of years for longer backpacking trips for my top, underwear, and thermal bottoms. I really enjoy the feel and antimicrobial nature of merino tops over artificial options. I find that artificial tops start to feel "sticky", less breathable, and even sometimes cause me to have rashes/irritated skin (especially underwear) after a couple days of wearing them. However, there are two drawbacks to merino tops for backpacking. One is that it's slower drying and the 2nd is that they are not that durable.
This nuyarn (90% wool and 10% nylon) used in kuiu's ultra merino tops dries noticeable faster than 100% pure merino and Rab Meco.
http://store.kuiu.com/ultra-merino-125-ls-crew-t-p/20015.htm
I've had a top for 8 months now and used it for essentially one month straight of consecutive summer backpacking in Wyoming and it is showing no signs of wear. However, Rab Meco 120 (same weight as the KIUI top I have) showed wear and small holes at the waist belt area after one month of intensive backpacking. Additionally, the KIUI top seems equally odor resistant. It worked out great hiking with this top in mid-summer even in the mid-80's and I never felt too hot/wet because of the shirt and it has worked great as a base layer when it gets cold when hiking and kayaking. For me the Rab Meco just seemed more expensive than regular merino with little or no advantage. I just wish that someone would eventually make boxers out of nuyarn. With the KIUI top, I could wash it if I had time in the evening, and it was dry by the morning even on a cold night.
You can learn about nuyarn here:
