JBoss EJB3 is written on solid product-level products like Hibernate 3.0 and JBoss AS 4.0.
However, our EJB3 implementation must remain alpha until at least the public draft is out (June?). THis is because well, the spec is a moving target. Yes, a lot of the API is probably stable, but it is not guaranteed.
As you've already noticed, there's still a lot of work to do with tutorials and documentation as well as unit and stress testing. They are growing, but we're still trying to catch up with implenting the specifications.
We do however offer Silver support on all our non-production releases of our software.