The BulletSim physics plugin for OS X as been updated to be at the same revision level as the Linux and Windows versions. The latest version lowers CPU load, and fixes bugs and issues. It can be found in the bin/lib32 folder of the OpenSim git repository as libBulletSim.dylib.
To update, shut down your OpenSim instance, replace the library in your installation and start your OpenSim instance again.