have a look at the ode applications on
www.ODE.orgThey showcase the physics engine quite well. I ran into one of these applications over an email before I ever met ODE properly. It was a game where you pushed a man down some stairs. A ragdoll affair. You got more points the more injured he was. Very macabre, but quite fun! haha.
ODE's performance seems to be pretty good. As for a java wrapper, well there are overheads but it runs pretty smooth on my apps. I am quite happy. If you write you java code with zero garbage collection or at least little enough to be able to call gc() between levels or something I reakon it could be up for commercial apps. Maybe not quite quake 3. But definatly Lemmings 3D would be possible I should think.