I've just been watching the video demonstrating Mortise Pal.
(refer to the post Mortise Pal is coming, in the Professional Woodworking Section, near the bottom of this menu)
The technique shown is to plunge a series of overlapping cuts, and then to finish the sides of the mortise by passing the cutter up and down both sides of the template. The results in the demo look perfect.
Today I was plunging mortises with a half inch spiral upcutter, 30 mm deep in American Oak, and using my homemade jig because I haven't got a Mortise Pal yet.

For what its worth I found that while plunging a series of overlapping holes made it easier on the router, the finishing cuts up and down the sides left the sides of my mortises looking like a series of shallow scallops (only a fraction of a mm, but quite visible. I figured that the cutters work better while plunging, and that the side cutting in hard wood is not nearly so efficient. I got far better mortices with taking a series of shallow cuts all the way around, advancing the depth perhaps only 4-5mm each time.
Maybe plunging a series of overlaps is okay for softwood, but shallow cuts seem best for oak. Or am I missing something