I found the best way around this was to make sure your not having to redeploy all the time. Make sure your using the seam hot deploy class feature for pojo's, facelets etc.
My app starts in jboss in 30sec on a quad core brand new linux box!! I only tend to restart every now and again !! EJB3 deployment seems to be the main thing.
this is a valuable hint but do you know, why startup time of Seam 2.0 has been duplicated?
Other posts in http://seamframework.org/tag/Performance have no further information. Even release notes (http://www.seamframework.org/Download) don't show significant changes that should influence startup this way.
In this specific case, the change in startup time is related to the change from Embedded EJB3 or Microcontainer to using Embedded JBoss - this is not the Seam startup time.