Just found Objectify on http://code.google.com/p/objectify-appengine/
The Google App Engine/J low-level datastore API is simple and elegant, neatly reducing your data operations to four simple methods: get, put, delete, and query. However, it is not designed to be used by the average developer:
DatastoreService persists GAE-specific Entity objects rather than normal POJO classes.
DatastoreService Keys are untyped and error-prone.
DatastoreService has a machine-friendly but not human-friendly query interface.
DatastoreService has an unnecessarily complicated transaction API.
DatastoreService is rather poorly documented. You get to figure it all out from the Javadocs.