1. Player names aren't saving (this was noted in another thread, but since there's a few more issues I figured I'd add it here too).
2. The "remove database" function doesn't seem to work perfectly. It removed my old database from the list but that database is still listed in the PokerTracker.cfg file (under the [Database] section, as Default). Not only that but my original database is also set in "PlayedHandsDatabase" (under [Import]) even though it doesn't exist. I'm not sure if this will have any weird side effects.
3. PT refused to pickup Stars even though the directory existed and was set correctly (under auto-import). I had to literally re-install Stars on top of my existing Stars installation for this to work.
4. PT isn't auto-updating my stats on the HUD. I have to manually open Cash->HUD Options and hit Apply for the HUD to updates hands. I have it set to update every hand. This is a big problem...
Other than that it seems to be working ok. Manual import ran at 300-375 hands/sec for 75k hands. Quite a big improvement over the earlier releases.

Edit:
5. I'm not sure if this is a bug in beta 21 or not, but I specifically have it set to "not import observed hands", but the mini-log window at the bottom of the auto-importer is saying that it's importing observed hands (for Stars). Why?