My last post initiated some related threads about glassfish, which are really interesting. The first news-item is from theserverside, second from infoq.
Btw. I used and use JBoss in many J2EE 1.4 projects, Geronimo is only interesting for J2EE 1.4 now.
I tried glassfish and was suprised of the quality gain (I know also the J2EE 1.3 RI which was hard to use - even in training .-)) and monitoring (admin console, call flow etc) capabilities.
Just try it out.