That, as is so often the case, depends on your circumstances. Maybe you can't use an EJB 2 container, then you'd be stuck with EJB 1. But there are so many benefits in EJB 2 ober EJB 1 that it seems safe to say you should go with EJB 2 if at all possible.
Given that EJB3 is on the horizon, why would Sun make us study EJB 1.1? Seems crazy! It is my experience that most commercial applications of EJB are EJB2. Still, ours is not to reason why we just have to go along with it I suppose.