<p>Should we add a tag for 'laser' for those of us who are attaching laser cutters/burners to 3D printers to turn them into 3D CNC. Or is this drifting too far off topic from "3d printing"?</p>

A good question. I'm currently using insights I obtained from mucking about with a 3D printer with Arduino Mega 2560 and RAMPS 1.4 to dive into retrofitting an elderly CNC router (but, as a router, still, not as a printer) with a new control system (presently thinking and have on order Arduino Uno R3 and Arduino CNC shield R3, we'll see how implementation goes on those) and was wondering if I could ask questions here that would overlap, or not, as I don't think there's a CNC/subtractive community similar to this 3DP/additive one in the ecosystem yet.
I actually started out thinking I could just use the same controller setup (there's plenty of stepper driver slots available, and going "dual-purpose" cut and print is potentially interesting) but it seems the official GRBL fork is not 2560 compatible, though there is a fork to try and make it so - it seemed more of a sure bet to stick with the "official" fork and the common hardware.
Likewise I've seen a bit of chatter about making Marlin switch-hit CNC/3DP, but I get the impression it's not all there yet, and I'm more interested in immediately usable based on current/past efforts than trying to develop new functionality my dang self.