i understand there are substantial changes being made to the internal data structures for upcoming iPhone 3.0 firmware, so I strongly recommend you do NOT use MusicBee to write to your iPhone if you decide to upgrade the firmware as it is likely the music database on the device will become corrupted as a result.
I'll provide any updates as i find out more.
edit: version 1.1 RC2 and 1.2 beta now support OS v3