I've used it before, but never owned it. The spin count seems to be accurate. The speed is not as accurate as a radar gun, because it calculates speed based on distance that you program, thus as distance from release to impact with the catchers glove (or in a case of a passed ball, something else) varies, so does the speed. The benefit here over a radar gun is that it is less intrusive (girls tend to freak out when you point a radar gun at them) and it does not require a third person to hold the gun.
It's a tool for data collection, it seems like a useful tool, to me, however given the price I think it's better for an organization or pitching coach then a parent of a pitcher.
Have it, and I would agree that it has it's most value when measuring spin speed, not as accurate as a radar gun for speed. Mine seems to register higher than a radar gun, most say that it registers a little low. Great aid for measuring spin progression for movement pitches.