Comment 3 for bug 367808

I'm not sure how this functionality used to work, but this doesn't seem like a bug to me. Acceleration doesn't affect the base speed of the pointer when you're moving the mouse slowly, only when you move it faster. So acceleration less than 1 is saying "when I move my mouse faster, make the pointer move slower relative to my hand speed" which doesn't ever seem desirable.

To change the base speed of the pointer relative to hand speed you need to look at the ConstantDeceleration option. In modern systems it's set in an FDI file, typically /etc/hal/fdi/policy/10-x11-input.fdi (which doesn't exist by default in Ubuntu 9.04). I've attached a basic version - so far I haven't worked out how to get it to take effect without a reboot. I've used USB IDs to identify the mouse, since this is an option I regard as specific to a given piece of hardware - a different mouse might need different settings. Obviously you'll need to update it with your own USB IDs.