I don't know whether it's an excellent generator or junk, but some of the claims on their website are absurd. (Directly connecting the alternator to the engine eliminates the need for a flywheel? The suggestion that such an attachment is novel, and not standard in virtually all small generators? An inverter that isn't directly run by a digital computer circuit isn't a real inverter?)
In terms of evaluation: if it starts easily, runs smoothly, and works properly under a reasonable load (at least half its rated load), I would tend to believe that all's well. Of course, a perfectly functioning generator may not be the right generator for your application, so testing it with the loads you intend to use it for would be even better if possible—I guess I'm mainly thinking of starting an air conditioner if you have one you're hoping to power with the generator.
