Why I love NHibernate:
I am rather please by the fact that a database schema change involving the creation of six new tables, three one-to-many relationships, and a many-to-many relationship (which includes a sort order on the join table) can be taken care of inside of seven easy hours. It probably would/could have been less, but I crafted the HBM and class files by hand and had a few typos which hide themselves well. This also included the time it took to create some quick integration tests to ensure that CRUD is working.
Now, of course, there are other changes to the domain that need to be done to deal with these new tables, but NHibernate frees me from paying a significant "database tax".