It's super-hard to find good large blocks of time to work on SQLAlchemy at the moment...but I did manage to get most of the major "whats new?" bits up on the wiki. I'm really close to pulling the trigger on a beta release, and we already have people running trunk. There's just a certain presence of mind I like to have before releasing that hasn't been clicking on weekends.
Read about the big new items and what to expect when upgrading, at http://www.sqlalchemy.org/trac/wiki/06Migration.