NHibernate 2.1 Alpha 1 Is Out!
Posted by Davy Brion on March 15th, 2009
Fabio just made the announcement. You can download the source or the binaries here.
And don’t let the alpha tag fool you… while we can never guarantee bug-free releases (who can?), 2.1 is very good already. We currently have 2 projects at work which have been using the NHibernate trunk instead of the 2.0 release for about 2 months now with no NHibernate-related problems 
Be sure to check the release notes to get an overview of new features, issues that were fixed, and some breaking changes.