A non-official patch has been pushed for Halo which you can get from here. For those who may play HaloMD, an update has been submitted for that as well. The patch tries to fix a bug causing Halo to crash on start up on Mavericks -- a memory corruption bug. Systems that are affected likely have a intel HD series card (even if the computer also has another dedicated card). I have no idea if this will fix 'halo being slow' problems. If you have the game and are experiencing problems, please give it a go and report back with what kind of system you have.