Every time after a Java EE spec is released it’s somewhat of a battle of who is the first to certify for that new specification.
GlassFish is always the first (by definition, as required by the JCP rules for a RI implementation), with tech previews/community editions of JEUS and JBoss following suit. These are however not (directly) supported for production by their own vendors.
During the Java EE 6 cycle, IBM was the first to come out with a supported and certified server, namely WebSphere 8.0. For the Java EE 7 cycle, the battle seemed to be between IBM and Oracle. Both of them are expected to release a Java EE 7 server soon. People are eagerly awaiting this, as Java EE 7 brings many improvements.
Surprisingly it’s the relatively unknown HITACHI Cosminexus Application Server that was completely silently (in Western outlets, that is) added to Oracle’s certification page. HITACHI themselves do mention this fact on their homepage, but otherwise there hasn’t been much news about this.
It appears that HITACHI is focusing exclusively on the Japanese market, but still this may be an interesting server to check out.