So I should stay away from Roton?? What exactly were they complaining about.. Accuracy? Overall quality? I did a lot of searching but didn't see anything that bad about them (probably looking in the wrong place).. They are pretty cheap so I guess it doesn't surprise me.
I don't need a super-accurate machine, but it does need to be usable. If I were to map out any linear error in the screws, and use oversize balls to reduce backlash (hopefuly to ~0.001) .. Maybe even a double-nut on the Z axis.. what kind of accuracy can I expect?