:-), I don't know that I've ever disagreed with Mariss, but a portion of that post is incorrect in the context of the above post. MACH3 and EMC both frequently use kernel and thread times that can be 40us to 50 us and easily have 10us jitter, not sub microsecond accuracy.
But I suspect the post is also out of context, it would make more sense if it was in respose to a suggestion of using USB without intellegence to handle the motion control, so maybe I'm not really disagreeing with him.
While 1ms latency is a USB issue, it's also kind of a myopic look at how to use USB. If you consider that you can stream large amounts of data via USB in some of the more exotic modes of USB, the latency essentially isn't a huge issue. Read up on isochronous transfers in USB.