We at The Looner's Chess Club are getting more and more inte low tech email chess and less into turn-based chess at fancy sites.
However, one iPhone app has caught our interest: Social Chess
Everything is very neat and well designed. The only minor thing to complain about would be the somewhat smallish player pool. It can take a little time to get a game started but once it is up and running all is fine.
All games are rated and you can email yourself the pgn-file after the game is over.
Another nice and somewhat under the radar chess site is Chessity. Chessity is basically another Tactics site but there are a few things that is somewhat interesting. The site offer a nice 20-minute drill where you are supposed to solve nine problems within 20 minutes. There missed problems and you are out. Another similar training activity is to "race" to nine correct solutions against other chess imnporvers (the same three strikes and you're out applies).
We have observed a little odd behaviour from Chessmaster lately. My Arch rival "Seb" has a rating that varies from time to time and without any obvious correlation to the results in the most recent games. Why is that?