I too am waiting for this feature to be implemented before switching to Mach4. The tangential knife support in Mach3 is buggy as hell, but at least it is there. Sort of, when the moon is properly aligned with Saturn. I sure hope they get this working right in version 4, I'm getting really tired of having my work trashed when Mach mysteriously decides to rotate the knife in the opposite direction than it should, even after correctly running he same g-code many times in a row and rotating it the correct direction each time. I'm a programmer myself, and let me tell you it is not very easy to get computers to behave randomly. They are logical machines that do exactly what you tell them and are very good at doing the exact same thing over and over, so getting a program to occasionally make random mistakes while doing the exact same operation over and over is quite an accomplishment. Then again, I've had loose connections on the driver board also cause this same problem of motors turning the wrong direction.