They're absolutely invaluable for aerials. When shooting with a film camera I use three, one for each axis, and they do an excellent job of making me look good. They work beautifully on boats, too.
As far as a ground set-up goes, I don't think they'd be worth the hassle. They're slow to react to operator inputs, take a long time to get up to speed, and, at least in aircraft, require a complex, dedicated power supply.