Just came across EitherMouse. It's working well for me so far
•Instantly changes settings when any mouse is used: ◦swap buttons
◦mirror cursor
◦adjust speeds
◦and more...
•Leave multiple mice on a pc and automatically swap buttons on each mouse.
•Have a left-handed and a right-handed mouse always connected and ready to use.
•Match speeds across different mice, ie touchpad and mouse with different speeds.
•Accommodate left and right handed users easily on multi-user or public workstations.
•Helps prevent RSI/injury issues by allowing seemless switching between hands.
•Quickly change mouse settings from system tray if only one mouse is used
http://www.eithermouse.com/