The combat cut makes it MUCH easier on the draw, especially when you have a high heart rate. You can draw pretty quick without it, but it's difficult to get your thumb in there for a correct grip without the cut.
I decided to save a little cash, and make my own cut. The problem is that I took a little too much off so when I reholster my 1911, the thumb safety will catch the edge of the holster.
FYI, you don't need a Dremel to make your own combat cut. I just used a sharp pair of scissors to make the cut, and then burnished the exposed edge with a wooden dowel rod.