In reply to Dave Hunter, Rock + Run: Some of the icebreaker stuff is aimed more at the fashion market, I agree. However the silkweight merino tops and the midweight ones are outstanding - they wick well, don't itch, dry suprisingly quickly and never really smell. They are also easily washable. I have a very nice silkweight T, the only problem is it's far too nice to wear in the hills!
I noticed Andy Kirkpatrick mentioned them in High recently, not sure if he's reading this thread. If so he may have some comments too.
The socks are available in both mens and womens sizes:
http://www.icebreaker.co.nz/product/rocksocks.asp#size
I run in the lighter short versions and telemark in the heavier weight ones. These are relatively slow to dry though.
Interestingly I also have a pair of freebie Fox River socks circa 1993 that are still going, in terms of longevity they've done well - if only the y weren't so uncomfortable to wear! They are the sock equivalent of the undead.
As for Icebreaker socks, I haven't yet used them for winter mountaineering as it was summer in NZ when I bought them, and not much snow round here now...