I think it would be better to save the extra time for learning EJB 2.x and instead start with EJB 3.0!
Unfortunately I don't know very much details of EJB 2.x but from what I know I can tell you that 2.x and 3.0 are VERY different! Also EJB 3.0 has lots of improvements which makes it easier to learn, too. It's not like java 1.5 and 1.6 where you have a common foundation with "only" a few improvements and extensions in the newer version. So I'd say it's not worth the time to learn EJB 2.x