My Java friends at University often balk at the lack of a O/R mapper for .NET. Of course, I show them a whole heap of O/R tools available, but then they show me Hibernate for Java. And, packed with its full OO support, with polymorphic relations, inheritance structures, and interface production, I have to hang my head and conceed :)
So, its great news NHibernate is in production, and now has an early pre-Alpha release available to download. Obviously, its not ready for full production, but what a great project coming since Microsoft decided not to include ObjectSpaces within the next version of .NET.
Open source and .NET, what a combination :)