Just to clarify this discussion doesn't mean that I regard Glassfish as the ideal platform for Seam development. JBoss is still the preferred platform because of all the support it offers (e.g. builtin hibernate JPA, automatic registering of EJB's in JNDI, etc) and better overall testing of the platform with Seam (well the developers are using JBoss to develop it !).
This thread should just let people know that if they do have severe performance problems (probably due to weak hardware) then there is a choice. But as always it is probably cheaper to upgrade the hardware than to pay someone to port the app to another application server.
Regards.