My team is developing a new service oriented product with a web front-end. In discussions about what technologies we will use we have settled on running a JBoss application
I would definitely recommend EJB3 over spring. We find that it's more streamlined, nicer to code in, and better supported. I have in the past used Spring and found it to be very confusing, and not as well documented as EJB3 (or JPA I guess at the end of the day)
I can't speak that much about spring, as I only tried it out for a few weeks. But my overall impression of it was very poor. That doesn't mean it's bad framework, but our team here has found EJB3 to be the best for the persistence/business layer.