Gavin King (Mr Hibernate) trashes what we call 'Object Databases'. This is excellent reading material and full of information why RDBMS's are still around after all those claims of object database vendors that their product is so incredibly more efficient
Read the article here: http://blog.hibernate.org/cgi-bin/blosxom.cgi/2007/05/23#in-defence
And remember the latest version of Nhibernate DOES support stored procedures! No more wizard generated SQL that is hard to debug because you don't know what it looks like.