I have one project using NHibernate 1.2. I know it\'s old, but I\'ve used it since I\'m working off NHibernate in Action, which targets that same version.
I\'ve been
Off the top of my head and mixing 2.X and 3.0 features... LINQ support, EventListeners (more powerful Interceptors), System.Transaction support, generics support, multiquery, future queries, SchemaUpdate (rather than just SchemaExport), much better HQL parser, ... Plus numerous bug fixes. A lot has been going on in the NHibernate world since NH 1.2...