Comfortable mouse tracking speed not available in system preferences The mouse section of the OS X version 10.8.2 system preferences has 10 different tracking speeds for my mighty mouse.

Unfortunately, the 4th fastest option is too slow for me, and the 3rd fastest option is too fast for me.

I've recently converted from a 21.5 inch iMac to a 27 inch iMac and I cannot recreate the mouse speed I've been used to.

How can tune my mouse's tracking speed, beyond the speeds available in the system preferences?
You can adjust the tracking speed on the command line through the Terminal:

defaults write -g com.apple.mouse.scaling x.x


Where x.x is the tracking speed, 5 being the high and 1 being low, e.g.:

defaults write -g com.apple.mouse.scaling 3.5


To reset it to defaults, use:

defaults delete -g com.apple.mouse.scaling


And it should reset back to the default tracking speed. Play around with the increments and see if that's fine-grained enough to find the tracking speed you want.