The toy is well built and a nice concept, but the main flaw is the WiFi range. The max distance is about 7 to 8 meters (25 ft), even without any obstacles. Beyond that, I'm always loosing control (without warning, as you don't have any signal strength indication). Both with my iPad 2 and iPhone 4S.
The toy creates its own ad-hoc wifi. This is useful where there's no network. But when you have one, eg at your home, it's a pity you cannot use it for a better range.
As it is almost impossible to control the tank in another room or a bit far from you, it loses it's interest. Same for sound : when it's a few meters from you, a larsen feedback prevents you to use sound. At a longer distance, you are disconnected...
Forgive my English mistakes, I'm Belgian !