I haven't run it. From what I had heard in the past it wasn't really complete but that could have changed quite easily. I've switched to linuxcnc on almost everything so far just because of its flexibility and to keep my machines consistent (I'm not completely there yet, it's got a steep learning curve). Mach3 was so buggy that I personally didn't expect mach4 to be a lot better, so I kinda steered clear of it.