For a while my whole media setup was working out quite well. I was using iTunes on my MacBook (computer I bought roughly two years ago to fiddle with Apple stuff) and streamed music via AirTunes to my receiver. The few times this caused trouble was because of a crappy wireless router. My Xbox 360 combined with Connect360 software for Mac OS X worked reasonably well for playing video. The only complaint I had was that the Xbox is somewhat noisy. Then my MacBook died and repairing it was too expensive. I decided to wait for a new MacBook Pro line as the MacRumors Buyer's Guide recommended, which gruber thankfully pointed out to me. While I was waiting Apple sued HTC over software patents. Why I Am Against Software Patents.
Long story short, thanks to a tip from runeh I bought an ASRock ION 330HT, installed XBMC on it, and have been very happy with it since.
I've been using the PlayStation 3 to play movies from the UPnP server on my Synology 407 NAS. For music there's a Sonos music player that I control using my iPhone or computer.
Very happy with it as well, main two drawbacks are that the PS3 cannot handle MKV files, and the limit of some 50,000 songs in the Sonos library.