From BlenderWiki

[edit] Physics and Game Engine

Fixed several bugs:

• python refcounting related and Bullet related (basic add/remove object support, bounding volume hierarchy).
• more game engine bug-fixes, hooked up 'formfactor' as inertia tensor tweaker, friction/restitution, more scaling related fixes.
• make clear that 'concave mesh' is really for static triangle mesh. too many people try to make it moving, it is for landscapes/static environment.
• rgidbody dynamics fixes (scaling again) to make Happy 2006 domino simulation to work.
  See happy_2006_4.blend or happy_2006_blend.zip for the baked dominos.
• remove constraint fixed, Bullet timestep now subdivides Blender game engine timestep, so it runs 60 hertz, SphereShape reverted to old style, so no support for non-uniform scaled spheres for now,
• fixed ApplyForce in physicscontroller, and crashing radar sensor