Oh, yeah, the whole reason I started back into the blogosphere: I saw a post over on the JPOX forum that I thought was worth sharing, just for the stir-the-pot factor. It's entitled "JPOX better than Hibernate according to Hibernate trainer!"
NB: JPOX is a JDO- and JPA-compliant ORM, and is the reference implementation for JDO 2.0.
In all fairness to Hibernate, clearly the most widely used ORM in the marketplace, it wasn't a trainer from Red Hat/JBoss/Hibernate; it was actually a Spring Framework trainer (no, not me, to my knowledge) who mentioned it. Perhaps the poster, Chris Colman, could expound a bit more on why. It looks like he's from Step Ahead Software and exPOJO, and does a fair amount of JDO and Hibernate work.