I was experimenting with backlash compensation (IMO its awful I wont use it). I had .0035 on the X and .0012 on the Y as best I could tell anyway. The z had very little backlash but thats only because it has the heavy weight so that the backlash doesn't come into play as much.
I have a few ideas in mind about using a double nut to remove backlash and compensate for wear automatically but its *much* more complicated than it sounds. Essentially the nuts that are there remain the same and can be used to remove most of the backlash like they do now. A second nut is added near the original nut and is mounted to its own slide with a spring pushing against it and the original nut for a "preload" of maybe 25-50 pounds.
Might even be able to estimate wear and remaining life of the pre-loaded nuts by measuring the distance between them.
I'll test my bobcad skills and get some kind of mockup to show what I mean but in the meantime I am interested in what others have done to minimize backlash.