JBoss (Red Hat) has yet to release a commercially supported 100% Java EE 5-compliant container*. There is a beta of JBoss 5 out. Hopefully they won't be 3 years behind for Java EE 6.
JBoss is more concerned with their microcontainer than Java EE x because that's what they say their customers are more interested in. I have never met any of those customers. But it does mean that Java EE is a second-class citizen in their world. As proof, their containers don't even ship in compliant mode; you have to tweak some config files to make it spec-compliant.
If Sun wasn't about to be consumed by the blackhole that is Oracle, I would recommend Glassfish.
- Red Hat does have a commercially supported 90% Java EE 5-compliant container. JBoss 4.3 is their "stepping stone" to Java EE 5 version.
