playchess.com has an unbeatable interface but you have to pay. I got fritz 8 ages ago and my membership ran out... I still don't play live games on this site, not because it isn't the next best free thing, but because I dont find a need for blitz matches because i would only play them on the internet
i found playchess.com about two years ago. the one that says or said, "cup of coffee included?" i still havn't used all of my free games because when i learned that it was a pay site i looked for new chess sites and found gameknot.com (a turn based site), yahoogames.com (a real-time site), and chess.com (this site). i have been using yahoo for real-time games but many people there only want to play 1-5 minute games, and if you play no time limit some people will wait nine minutes for a move hoping you will abandon the game.
i, too, only find the need (well most of the time) to play blitz games online. but blitz is something different; it keeps me on my toes.
I have just discovered the live beta chess under the play tab in the taskbar thingey. I LOVE IT. It allows me to work on my timed games. Another site I play on allows me to play timed games too, but for some reason this was way better. Thanks for making chess.com such a user friendly place! Keep it up.