If you use the mouse wheel to zoom while the tool is cutting the part you can greatly change the cutting speed.
Lots of the time I want the sim to go quickly for a little bit then slow it down and this just so happens to correspond to the zoom factor. When the part appears small the sim runs very quickly. But wheel in close and it slows down so you can watch the detail.
If the sim is still running too fast you can slow it down with the slider and you can change the accuracy from .02" to .002" or smaller.