USB Overdrive has been the dominant 3rd party mouse driver for quite some time and been an absolute necessity for more demanding users due to OS X's scarce customizability and poor handling of 3rd party mice and keyboards.

While its previous versions have been limited to controlling and customizing the mouse, 3.0 can also control keyboards, effectively eliminating the need for other drivers such as Logitech Control Center, drivers which often has proven to be unstable, incompatible and incomplete.

Highly recommended.