A local rink has a Sparx in addition to a traditional Blademaster. One guy says that the vacuum does not work all that well. Of course he is biased because he is a Blademaster guy.
My biggest trouble with mine is sharpening Step Extreme blades. I had quite the learning curve and nearly sent back the machine! I devised my own way to get the Step Extremes into the carrier and not stop in the middle of a pass. That being said- the only Step Extreme I will sharpen is my own.
I now charge $10 if they go more than six weeks out because I find that the more rounded over a blade is (especially if they mess with their blades with some of the self sharpeners in between), it takes 10 passes to get a good edge. I am trying to incentivise customers to sharpen more often, as it is more cosistent and easier on my wheels.