Here is a short update on the current project status. We're heavily developing towards a 1.0 release that will bring lots of enhancements like improved inheritance mapping and lots of other stuff. We're especially keen on making this release as stable as possible and on polishing the documentation.
Until then we strongly encourage everyone to use the 0.9 branch that can be found here: http://svn.phpdoctrine.org/branches/0.9 It's a feature-frozen branch that recieves bugfixes. There will be no changes that break backwards compatibility in this branch.
The current trunk is under heavy development, so please don't use it unless you are developing on Doctrine's source code or you are just very curious.
When the time for the 1.0 release comes near we will provide a migration guide and do everything possible to help you take the leap from 0.9 to 1.0.
PS: At this point, the the whole Doctrine team wants to apologize for the version mess you've gone through (and are still getting through). We really messed up in terms of release management mainly due to the lack of experience in this area. This stops here. 0.9 will stay and it will stay for a while. We're not going to rush releases again.
Thank you very much.