Mr_Cellophane Does it do anything that you can't do on the asiair?
Yes, you can hard press on one of the slew buttons and the stepper motor will keep running. In the ASIAIR, you need to keep tapping the slew button. Probably not a deal breaker.
I have multiple EAF, but only one hand controller. Because of the hard-press function (don't know why the ASIAIR does not implement it) it comes in quite useful when initially finding focus on a new set-up.
But you don't need one during "normal" operations.
Plus, it has a disadvantage in that there is no way for you to set the step durations or max step value. You still need a computer to do that.
Chen