I was tempted to try these out, while investigating the stepper/encoder combo I found a few other options one of which is to use a motion control card like a kflop or galil.

Kflop has its own program like mach3 or you can use the kflop as a plugin within mach3. You still need to add your own encoders, but this gives you options to use linear scales or rotary encoders. Nothing beats a mechnically backlash free and super rigid machine but it would be an amazing breakthrough if systems like these could make up for some of the sloppyness in machine builds.