Exercise Ball Chair?

I'm contemplating bringing one of these into work:

Maybe I'll use it as a desk chair for most of the day.  Sitting on them helps with balance and posture, and keeps you alert.  Face it, if you start to slouch or doze off from staring at all those numbers, you're going to fall off!

I think I'm going to go for it.  I have a sort of corner desk so there'd be room to store it underneath without it rolling away.  The only worry I'd have is fending off the weird looks and comments I'd get from my co-workers.