I'd like to say thanks to Jazz for recommending the smooth stepper to me, even though my original post on the subject was about servo motors!

I've got it installed now and cut a few things. The increase in accuracy is quite noticeable, even running at a higher speed. :)

At the same time as installing the ESS I did also upgrade one of my motor drivers so that will no doubt help, but I've gone from rapids at 6m/s to 10m/s and cutting from 4m/s to 6m/s and still seeing higher accuracy.

Worth every penny.