I have recently started exploring EJB 3.0. I am using the latest builds of Glassfish, Sun's OpenSource Application Server. Glassfish contains an OpenSource version of Oracle's Toplink product.
I had stayed away from EJB so far, as I was not convinced that the benefits of EJB outweighed the complexities it introduced into code. I had been looking at alternative light weight frameworks such as SpringFramework as a substitute for EJB. EJB 3.0 has however converted me. In my view, once production implementations of EJB 3.0 are available, there will be fewer occasions to use alternative frameworks.
As I learn more about EJB 3.0 and Glassfish, I will post my findings here. Stay tuned.