I'm using v3alpha7 on two different empegs, one in the office, one in the car. I've only ever ripped my own discs to Ogg Vorbis files, that's over 12000 songs on the unit in the car. Mostly it's been working fine ever since the v3alphas were released, there have been some minor problems, but only one problem that's ever affected playback, and that was with an earlier release, v3a5 maybe?
All of the other issues are much easier to live with. There's the songs getting marked problem that's been mentioned before. There's the song name being changed to "various" on occasion, this has also been mentioned before. And every now and then I have a problem uploading songs, and the connection dies. It's on occasion been a bit of a pain to cleanly recover, needing to get in via telnet or the serial port to run fsck. And there's been a few issues with emplode.
Hydrogenaudio.org and rarewares.org are the best resources for ogg stuff, including hints about reccomended versions and pentium 4 compiles.
--Nathan