In a number of competitive FPS communities, there seems to be a stigma against high DPI. Many gamers run their mice at 400 DPI for various reasons. In traditional flat/no accel cases, that's fine, but I believe it's less than optimal for povohat's driver.
Important note: some mice have known tracking issues/inconsistencies/jitter at higher DPI. Google your mouse and see if people recommend avoiding certain DPIs. If your mouse is bad at 5000 DPI, but it's good at anything from 400-2500, use something like 2500 or a multiple of 400 to make the conversion easier.
That aside, here's my argument for higher DPI: If you are running your mouse at 1000hz and 400 DPI, chances are that the fastest you will realistically move your mouse will only show, for example, a change of 15 counts (or dots). Since the driver reads in how many counts (an interger value) and uses the acceleration settings to change it, what does that mean? Well, your entire acceleration curve has to be packed into the range of 1 to 15. Most of the time you'd probably be moving your mouse and only get a count less than 10. A small change in the speed you move the mouse could result in a larger jump in sensitivity than you desire. Effectively, you've got a bunch of step increases in sensitivity. It would look like this: