I thought I was going to go sit through a painful bashing in a session subtitled "Evolution from SQL to OJB to Hibernate" -- but it wasn't =) The session actually got reasonably technical, showed real examples, etc. Their OJB info was a touch dated (they didn't know about anonymous keys) but was pretty accurate in general, and they definately know their stuff. Not surprised, they have been using it probably as long as I have =)
They pointed a few very nice things H does which we don't (though I am not sure of one, need to check as it is a config piece I never use). All in all, good session. Hibernate came out smelling better, I think, but it is better in some cases (er, when you really like SQL ;-).
The main thing I really walked away from was the incredibly importance of perceived project momentum. They pointed out, honestly, that momentum on OJB is not as high as on Hibernate. I agree. I have been working to change that, and believe OJB momentum is ramping up again. We had a really ugly 1.0rc roll. Ugly ugly. Basically we broke the key rule of "release often."
That said, everyone on OJB has been holding onto code waiting for the 1.0.X (bugfix) branch to be made so we can start cleaning up a lot of stuff in the 1.1 branch. With the release of the JDO 2 draft spec we can start looking at that. They got rid of the bytecode enhancement requirement, yea!
A huge thing that they touched on but didn't really explicit point out is that a big difference between OJB and Hibernate is that OJB wants to work with standards and Hibernate wants to become a standard. The things that are important to us are not the same as the things important to the Hibernaters, and that matters.