The main problem of mouse movement in Mac OS X is not acceleration — it’s lag.
By that I mean a delay between receiving movement data from the mouse device and rendering the on-screen cursor. The lag of a Mac OS X cursor is at least twice bigger than Windows’ cursor and yes, a human eye can surely notice that.
I mentioned acceleration because a lot of people often confuse it with lag. The truth is, in Mac OS X you can change acceleration to whatever you want using many programs and techniques. In ControllerMate, for instance, you can manually draw your own acceleration curve.
But it’s all pretty much useless as long as mouse movement is literally retarded, because it takes a lot of time for your brain to get used to it.
The problem I’m talking about affects all mouse and touchpads since at least Mac OS X 10.4 Tiger. It still exists in Snow Leopard and Lion.
The problem is caused by a bug somewhere at the windowserver level of Mac OS X, and not by a mouse driver. You can supposedly avoid the issue by disabling QuartzExtreme.
The problem is as well closely related to the cursor jumping issue that has alone been fixed in Lion thanks to all our bug reports.
The problem has been confirmed by an Apple engineer. I’ve also heard that they are supposedly working on a solution. The timeframe is unknown though.