I read Sindre mentioning that we might see a beta release shortly. ( the exact term I guess was in a week or two, and that was two weeks ago

)
Upgrading is a piece of cake. Just drop the new tar.gz in the same place as you did the first time, extract it and restart subsonic.
PS: If you have done any modifications to the subsonic.sh or something like that you might want to make a separate copy of that and do the same modifications to the new one.
If it's a vanilla installation you do not have to do anything
All settings, statistics and so forth are stored in the database which persists an upgrade.