JRebel 3 is finally out! http://www.zeroturnaround.com/news/jrebel-3-0/
I have attached a very detailed tutorial on how to use JRebel 3.0.1-SNAPSHOT with Seam 2.x hotel booking example deployed on JBoss AS 4.2.x. The tutorial demonstrates how to add a local interface method to the HotelSearchingAction SFSB as well as adding an @In annotation and hot redeploying both changes without a build/redeploy of the EAR and/or server restart.
If you find it helpful, I can create a screencast demo of this tutorial as well. In the future, I will be doing a similar tutorial for a Weld example.