Daniel Bevenius has written an excellent migration guide covering several of the possible pitfalls when migrating ejb applications to JBoss 7. If you have an interest in JBoss AS I highly recommend you checking it out. Daniel will keep adding more pitfalls to the guide so make sure to check out periodically. https://github.com/danbev/migrate
Daniel Bevenius works as a open source developer at Redpill Linpro and a committer on the JBoss AS 6.x, JBoss ESB and the SwitchYard community projects.