I have an FX-20, and it is a good cutting machine... The main issues that I have with the machine (i.e. wire threader, and water supply) have been worked out in the FA, or so the Mits salesmen informs me. Mitsubishi definetly has a good handle on EDM, IMHO they are probably the best machines out there right now, although I heard the new AGIE PROGRESS is supposed to be one wicked mofo... but I have'nt seen it in person yet.
I ran a Robofill for a few months, awhile back and maybe it was just that machine, but I was not overly impressed by it. Just my 2 cents.