I have seen these in use at RV dealers, they use them for the really tight areas where they can't get the fork lift in. They don't move very fast and have massive battery packs.
What you see on ebay looks to have about half they battery power that the ones I've seen and they have a motor that is bigger than a 3000# ATV winch. I'm a little sceptical on the claimed weight capacity and the prices for the materials seem on the low side.
For my money the front mounted hitch is a better solution and you have it with you where ever you go. There are times when I wished I would have had the front mounted receiver to get into a tight campsite.
