Hello!
I have tried it out for 6 month, and a must say that it is quite OK and exciting. It is a bit tricky before you get use to the standard java 3D classes but they are quite useful. And of course this is really nice for game-programming but remember to program effective so the RAM doesn't overflow.
Java 3D at Sun also provide a tutorial in pdf, 7 chapetres a guess. That tut covers the basics and took me 4 weeks to read and understand.
They also, on the same site at sun where you can download the tut, provide a mailing list with a lot of people that likes to help you out. I guss perhaps they delivers 30-50 mails a day.
A good site is
www.eyeone.no, if you become a member you can play a couple of java 3d games, my favorite is Burning metall 3D.
Best regards
Fredrik - Sweden