In the recent past, I've been eying JBullet and/or jMonkeyEngine and jME Physics for robot simulation. I think these could work, but I'm starting to like the idea of Blender instead. Blender is an opaque interface for newbies like me but still a lower barrier to entry for so many features than what I find trying to learn jME. At least for me right now. And I can do Python, too.
One concern I have with Blender is the GPL license, but that's not an immediate concern. I do love that I can download a binary easily on different platforms. And it might be interesting to make a network (or even web) server driven system with it, anyway. Easy way to allow for different languages, too.
Here's a nice detailed investigation into the use of Blender for robotics, by the way.
(Oh, and if you've heard of it, I might like Gazebo more if they distributed binaries and/or didn't try to make it so hard to build. Talk about having a billion dependencies on the latest version of everything.)