One reason I like the idea of servo steppers is because I find the machine sometimes loose steps when pocketing circles. When it goes to the centre it needs to change direction really fast to keep constant velocity. It then loses position slightly. My current solution is to slow the feed part way through the operation as it nears the centre, but at the moment that means manual g-code edit for me. I might also want to machine a whole sheet of detailed nested parts and then finish off with the through cuts so vacuum is maintained until the final cuts, but doing so much work across the sheet and then eventually coming back to the first part I find I may be out of position very slightly.