I need to write a Java-based web app (it has to be Java because of i18n and scalability issues my employer has with Rails) and I am looking at tools that increase my mileage. Under consideration where Seam and AppFuse, but what made me give Seam a shot is this video: http://www.jboss.com/products/seam/SeamHBTools.html
While I do not need to write a CRUD app this nicely shows how to actually get started without all the plumbing one usually has to do in Java EE (and even then there's some left). Anyway, I'll keep you posted on Seam.
Related to my research on this I came across a thread on the Rails mailing list. For christ's sake! It seems that the converted Java-guys are now Ruby-zealots that now find their pleasure in bashing Java EE. That's a shame because the Ruby community was so well-recognized for being friendly.
PS: if you also need to make up your mind about AppFuse and Seam I found Matt Raible's comments helpful (Matt is the project lead of AppFuse)