Many people think that the newest JPA is always the best choice now that first EJB 3.0 implementations are released.
JPA is a subset of Sun Microsystem JDO 2.0 standard. JPOX team published a matrix to compare their.
Today Freshmeat wakes up my email account with the new version of JPOX 1.1.4. I'll try it tonight to release it in the next RomaFramework distribution.
Congratulation JPOX team, the best ORM tool I never used. If you cannot use a pure ODBMS, JPOX is the best choice to work with objects and a Relational DBMS. With no doubts!