I have been an avid backpacker since '89. I did the "tech" bases for years. I tried merino and have not gone back. one reason is that it gets stinky quick. The main reason is I do not get cold when stationary.
I currently prefer Woolpower 200gram as my base top as it is easy care at wash time. The Smartwool is great for that too (I use this as my bottoms), but the Woolpower has the extra length in the back for kidney coverage.
I am switching over to almost all merino (or other wool) for layering this year due to my experiences. I still keep 800-900 down for vests and sleeping. (Hammock convert BTW, no sore back in the AM)
Ordered the last Evening Stand Brown pullover the Asbells had today, and plan on making a trip to REI to pick up a Smartwool TML Midweight this weekend.
The big drawback is wind, but that can be overcome with a thin wind layer.
As far as economics/price:
Right now REI has all Smartwool base layers, gloves, hats, and socks on sale for 20% off. Orders of $50+ are free shipping. So a midweight bottom and crew top are both at $64. The zip top is $72 and the boxer briefs are $45. Assuming bottoms and a crew top, that is less than $130 delivered--or about the same price as the Woolpower top after taxes. Boot top bottoms are $4 cheaper if you use high insulated boots.
I have been a Smartwool fanatic for years because of durability and ease of care. Their socks last me 3-4 years of everyday use November - April (all I wear when it gets cold)
The Minus 33 midweights are also on sale at essential apparel and are about a two thirds the cost of the Smartwool, but I do not have personal experience with that brand.