I wore these for a month-long sailing trip across the Pacific. I basically didn't take them off. My boots were perpetually wet, the outer layer of the socks was wet but my feet stayed dry. They didn't always _feel_ dry, as it is difficult to tell the difference between cold dry sock and cold wet sock, but investigation always showed that they were working. One warning, accidentally putting them in a Hot wash in the marina launderette will completely ruin them.
These socks in my experience are the best waterproof socks on the market. I work outdoors in all weathers after 5 hours of heavy rain my boots are waterlogged but the socks are keeping my feet dry and warm. The down side however is that they can be a bit too warm in warmer weather, but I am willing to live with that.
i've just returned from a 2 week expedition in the brooks range mountains in alaska. i took 2 pair of these socks with the sealskinz thermal merino liner socks. temperatures got as low as -40c. my boots ended up sodden wet every day and my feet stayed bone dry. i can't recommend these socks enough!
As a 6'4" man I'm used to uncomfortable socks with insufficient padding and ones that are too small.
I was worried when i put these on a first as they felt a bit tight but they stretched out quickly, I then had 16 hours of the most comfortable dry feet that i can remember, I cannot recommend these enough they are utterly amazing