I just built a new cnc router for cutting steel with high precision, the design is based from the MV3 with a few modifications like supported rails and a base. I've attached pictures of the results on aluminum and steel. I have things squared up now, I just need to glue everything down to prevent any play.
As far as accuracy I have gotten +/- .0005'' on a 1''x1'' square with light cuts on pine. I also want to put a clear hood across the uprights to capture dust inside and reduce noise. I spent just over 500$ for the entire setup without software and the computer. I am hoping to put up plans for this design and maybe make a few kits once I perfect the design.