Apple - How to disable mouse acceleration in Yosemite?

It turns out Yosemite enables mouse acceleration by default. it can be disabled by typing this in terminal:

defaults write .GlobalPreferences com.apple.mouse.scaling -1

After changing this setting in Terminal, you'll need to logout and log back in to your Mac. Relaunching Finder will work too (option + right-click on Finder icon in dock -> Relaunch)

Even with mouse acceleration turned off, OS X uses an 'acceleration curve', which makes the mouse slower and the movements less linear.

To disable the acceleration curve/set it to a linear one, download Steelseries Exact Mouse Tool, open it and set it to 'always on'(there will be an icon in your menu bar).

It doesn't just work with Steelseries mice, I use it with my razer mamba in combination with their drivers and it works perfectly.

USB Overdrive remains the best way to control mouse speed/acceleration in OS X, in my opinion. Apple's mouse driver is appallingly bad.