Just a warning, I'm a huge newbie to Seam. I've used EJB3 via Netbeans & Glassfish, but my interest in Seam won't let me stay away from it. So if some of my thoughts are way off, it's because I'm new.
Putting aside my hard time figuring out Seam, I really am impressed with the features (I love the xml completion). But, I can't shake the feeling that for $99, it seems like I got an IDE that just wraps seam-gen calls.
A lot of my "wants" for JBDS stem from using NB for a while, but here are some of my thoughts:
-I'd like to see a dedicated command to generate a EJB3 Entity without having to go back and delete the pages that seam gen creates in "view".
-When the project is removed from "Modules" in JBoss-4.2, it doesn't undeploy (where is the Undeploy option in JBDS?)
-I'm dying for an OS X version to come out (I've heard it's due Q1 of 2008)
Hope that helps you out. Let me know if you have specific questions about it and I'll try to answer them for you.