Version: (using KDE 4.2.2) OS: Linux Installed from: Unspecified Linux there is no check box in the mouse options to turn off the involuntary extra acceleration as one moves the mouse faster. in windows xp there is a check box named "enhance pointer precision". it simply has to be unchecked and your mouse responds in a kind of 1:1 way. its not about the mouse cursor speed, but about the extra acceleration which is not of a lot of use to people which don't use the laptop fingerboard, but a mouse.
*** Bug 189736 has been marked as a duplicate of this bug. ***
I always used to set the 'threshold' to zero to disable acceleration. An explicit setting might be more intuitive for the GUI though. In kubuntu 4.9.3 I've noticed that using a threshold of zero sometimes results in the mouse cursor jumping to the edge of the screen. Presumably this is some kind of bug involving incorrect activation and 'some distance divided by zero threshold = move infinite distance'?
These are issues in the evdev mouse driver itself, not anything we can change in KDE code. With the more modern Libinput driver, you can indeed fully disable all acceleration.