Remember that the layout of the data partition has changed. Being able to switch between v2 and v3 would probably result in a lot of broken databases.

not necesarily a lot of it. they use different databases in /drive0/var (database and database3), and as far as i can tell, going to alpha3 didnt wipeout ALL of the scratch partition. all my PLAYS data is still there. now, my other settings such as bookmarks, eq, and marked files is a different question.