I have an optical mouse (a Labtec laser thing) whose speed I can't get configured sensibly.

The only mouse configuration tool I know of is 'xset m'. 'xset m 1 1' is too fast a setting for precise work; but if I set the first parameter below 1 (say, to 4/5), the cursor does not move at all if I move the mouse very slowly—which also makes it impossible to use the mouse for precise work. It seems like a rounding error bug of some kind.

What can I do? What other tool can I use to adjust the mouse speed?

My ancient ball mouse, which just gave up the ghost for good, was somehow inherently "slower" so that I never had a need to tone down its speed.