Everything is now a POJO... so some of the design patterns from EJB 2 are not valid any more.
- Value Objects...
You don't need that as you don't need to convert your POJO to a POJO.
Lots of the events from EJB2 are not needed on EJB3. And even if you need then you can simply use an annotation
- Server State on EntityBeans
While you could have server state on Entity Beans, you can't have them on POJOs. (You would serialize useless information needed on the client).
You will probably find some tools that will "convert" your application to EJB3, but my recommendation would be don't use them.