Not bad, but not great.
Took a couple of tries to get this working as the battery connectors are not completely flush, but once going it operates fine. The main problem is that the motor is quite noisy, so our 2 cats aren't quite sure what to make of it. They follow it everywhere it goes - and it does move quite a long way, rolling itself in and out of corners - but won't quite chase it or dare to pounce on it. However, it does certainly keep them occupied. If your cats don't mind chasing noisy things, it might be the greatest toy ever, but if they hate them, it would be terrible as they'd be hiding from it the whole time! Anyway, it's a 3 star for us - buy it or not depending on your cat's noise tolerance.