It appealed to me because I don't like having to buy batteries or deal with replacing batteries. Also, I like not having to worry about it not being completely waterproof into the battery compartment, or having to take out batteries when I clean it.
However, it'd be better if the charger would be more stable. If I have it charging on my bed, a slight shift can make the charger rotate on the curved base and stop the charging. That's annoying. I also wish there was a clear readout of the current charge, which I realize could be difficult to do and maintain a sleek design.
Also, I was reading the packaging, and noticed that it says that it will wear out and be unable to charge at some point. And it says that you won't be able to replace any parts of it. So once the rechargeable battery/motor/whatever runs out, you have to toss out a perfectly good toy. I wonder when mine'll wear out, if I'll get a good life out of it before it's gone.