A lot of people here (including myself) have praised Darn Tough Socks. For the first time I got to take advantage of their unconditional lifetime guarantee. A few weeks ago, my first pair (merino wool, micro crew, cushion, hikers) developed a hole in the bottom of the heel. I filled out the form from their web site, mailed them in, and got my replacement pair yesterday.
These go with my other two pairs of non-cushion socks. I figured I should have a second pair for hiking, so I bought a pair of the special ATC edition micro crew merino wool cushion socks. They are on sale at Socks Addict and I got an extra 10% off with the promotion code TP1406, plus free shipping.