Couch-Surfing

I discovered this website (http://www.couchsurfing.com/) last night, and immediately decided on an adventure or two.  In the process of deciding, with a couple of friends, where we should go, and for how long.  Somehow, being university students in the midst of a recession, we are producing budget plans to go to Warsaw, Amsterdam, Prague, Thessaloniki etc.

Has anbody here had any experience on sleeping on total strangers couches in strange countries, and would they share their experiences?