I've just found out that NHibernate 1.2 now supports, beside many new features, ICriteria count.
This feature is very important specially for asp.net 2.0 applications that work together with the object datasource. This is exactly the code that our asp.net 2.0 Templates in GenWise was needing to improve performance.
If the user did not added some filters some "big" tables could take quite a lot to load just because we could not page the count. The GenWise factory does support paging of the result by calling the appropiate ISession methods .
This will be included in the next update to the GenWise NHibernate Templates.