I don't think you can 'do anymore', but obviously its a lot easier to work with and they work great with EJB 3 entity classes - mmmm no more parallel value objects.
There are some old 2.1 methods that will now throw exceptions if called, and some interesting features with nested stateful session beans and extended persistant contexts.
The primary motiviation for EJB 3 was to make the development and client models easier, so we are actually prouder of what the developer does NOT have to do rather than adding things to the list of stuff that you can do. We did end up with some things that fall into the category of "stuff you can do now that you could not do before", though. One important one is interceptors. They allow interception of business methods and provide the developer, or a layer above the developer, with an aspect-level ability to cross-cut a business API.