Do you feel like having "cycling specific" socks makes a real difference?

A friend keeps telling me that I should buy some "cycling" socks. He is the same guy that turned me on to clipless and that sure was a hit. I just have a hard time justifying how a pair of socks could make any appreciable difference over the cotton ones I am currently wearing....I mean, in essence I will get two socks for the price of one, it doesn't matter WHAT I put on my left foot...but anyway, cycling socks worth it?
What do they do better?