The 0.9 snapshots are only for people that want to use latest features, but this version may still contain bugs.
You can look at our NEWS file (http://svn.berlios.de/viewcvs/serendipi ... iew=markup) to see what's new in this version.
Upgrading from 0.8 to 0.9 is the same as upgrading from any version to any version (like from 0.7.1 to 0.
For SVN information please read http://developer.berlios.de/svn/?group_id=2573 and the referenced links
Regards,
Garvin