I've done a lot of Struts development. The biggest obstacle to using EJB 3 in a Struts application has been the fact that it needs an Application Server that supports
Java EE 5. Big companies are very conservative, and I have yet to do work for a client that has made the move to a such a server. So, as much as I'd love to use it, I can't until my clients decide to join the twenty-first century.