I know alot of hikers use these because they don't want to deal with gore-tex runners that keep water in. i think the general thought is to wear them over your socks. Think of taking a goretex boot/shoe but having it be modular. You can put on the goretex socks when necessary. I haven't used these myself, but I have used plastic grocery bags over my socks in a pinch and they worked really well to keep my feet dry in sodden shoes. Try searching through threads on backpackinglight.com, thats where I heard about them.
"Yeah, I just stare at my desk; but it looks like I'm working. I do that for probably another hour after lunch, too. I'd say in a given week I probably only do about fifteen minutes of real, actual, work" - Peter Gibbons
I have used $10 neoprene paddling socks for biking in the rain with running shoes. It keeps your toes nice and dry, but I wouldn't want to stay in them for more than about 6 hours because it keeps all your sweat in. Some mountaineers use them in conjunction with antiperspirant. I have doubts about how breathable Goretex socks could actually be, especially if they are immersed in a soggy shoe. I would bet it would be about the same as the neoprene socks.
Many folks swear by bread bags (there is actually a summitpost gear review for them).
I often use neoprene socks for one-day trips in transitional times of fall and spring. You can get 3mm versions that are ankle-high; be careful, as cheaper varieties are made with seams that can chafe. I give the seam stitching a very light urethane coating, else the stitching breaks and the socks fall apart. In neoprene alone, your feet will be wet all day, and will look like they have been in a bathtub. They can get really cold at the end of the day if your shoes are sodden.
Neoprene socks take forever to dry, even in warm weather. You have to turn them inside out several times to get them really dry. It seems that you could just change the inner socks a lot with the goretex version, and wipe out the insides with a towel.