I noticed upgrading my ATi graphics drivers to the latest version improved framerates, so I wondered if improvements would be made if I upgraded Microsoft's Logitech Optical Mouse drivers to the official Logitech drivers and install it's control panel. Using the control panel, you can disable mouse acceleration and override the OS mouse settings for those you specify in the control panel.
Aim precision is much better now in Nexuiz, and turning is much easier.
I don't know why I did not think mouse drivers could be a problem, but learn from my mistake, and get the real drivers for your mouse if you have not done so already, they're much better.

My will be done.