This product came up in a thread I didn't read until tonight. I have one, and I love it for moving my boat trailer around in close quarters. I modified it, and modified another for my friend at the lake, so the ball height would be about the same as the hitch on a truck. It's an easy mod for anyone with basic welding capability, and it saves a bunch of cranking on the tongue jack. It also solves the problem of changing ball sizes: there's ample room for a long-shanked ball with the mod. Photos here:
I've had no problem with the tires going flat and I did this in June of 2005, use it every summer at the lake. If the tires on the one I did for Ted have gone flat, he's never mentioned it. But then, he wouldn't. He'd just reinflate them.