After about 6 months, we have a new stable release of NHibernate. The full details are here.
I would strongly urge you to upgrade, but be aware that this is not a drop in replacement, there is a migration guide available. From experiance, it takes about a day to convert a reasonable size application to 1.2.
Favorite new features:
- Filters - (I really wish that I had them when I started my previous project)
- Generic Collections
- Database generated properties.
- SQL Dependencies for NHibernate's cache