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.

Perhaps your polling rate or DPI changed. SetPoint, for instance, overclocks the USB speed by default. Or it's just placebo effect. It's also not like you can't disable acceleration with the default drivers.

I'm using SetPoint.

If you weren't before, then the USB polling rates have increased. Also, at least for my G9, SetPoint uses the Windows drivers by default.