Earlier this year I started trying out some "free" webservers that offer correspondence chess. The first one I tried was GameKnot.
After registering I put out a "seek" for three games. Within a day or so the seeks were answered and the games all started. Unfortunately, only one game finished.
GameKnot has several convenient features. One feature allows a player to be immediately notified with a browser pop-up when a move is made by an opponent. *The above games are courtesy of GameKnot scripts if a player wishes to publish their games. The interface is nice and smooth once one is used to it.
There are problems. My rating was never adjusted. I was assigned a 1200 rating, beat a higher rated player, and still reside at 1200. Only one of three games finished. One game timed out after two moves, another after eleven moves. As a comparison, on ICCF's "serious" chess server, only one game eighteen I have played has been abandoned by the opponent. In my games on ICC zero games have been abandoned of the six I have played recently. When I played ICC correspondence back in 2004, none of the games I started were abandoned by opponents.
I was not fond of the time control options. I prefer the ICCF and ICC method of moves in a period of days, not days per move. The accumulated time does not roll over under days per move as does the former time control.
My overall experience at GameKnot was pleasant. A determined player could probably find more opponents to stay the course of a game than I did.
On a scale of one to ten, GameKnot would get a SIX from me, above average, but not up there with the "serious" correspondence servers.