The NHibernate Facility supercedes NHibernateIntegration and integrates with the new Transaction support. Please read http://stackoverflow.com/questions/4010265/how-to-let-nhibernate-retry-deadlocked-transactions-when-using-session-per-reque before using, it will help you.
Is it possible to support .NET 3.5 in the NuGet package or are there dependencies to .NET 4.0 only stuff?