I don't yet know about durability (which is something I've had a problem with in socks, in recent years), but they are very comfortable.

July 2015 -
I purchased another package of these, but I think I ended up with a smaller size somehow.  I always intend to get size 10-13 (I wear a size 10.5 shoe), but these are very tight and uncomfortable... package *says* size 10-13, but I don't believe that is what I have.