In OS-X, it has a rather aggressive acceleration curve for mice.
Normally, this works fine.
But if you use a gaming mouse (like Razer) then you probably don't want the acceleration. It can cause things to become jumpy or otherwise misbehave.
This is originally code found on http://forums3.armagetronad.net/viewtopic.php?p=196564#p196564
I just put it into an xcode project, removed the warnings and got it to compile.
I wanted to make sure I could find this code again if I had to re-install everything.