Great hit!

This really does hit hard, so long as you have at least two spectators. More would be better. You *can* perform this for just one person, but you need a camera to record everything, and it won't be nearly as impressive.

It requires precious little setup, and you really can predict just about anything; numbers, colors, shapes, simple pictures, etc. You're limited by your own imagination and creativity.

Pros:
Simple
No gimmicks
~30 second setup
Uses very common, very inexpensive items.
Very genuine feeling

Cons:
Doesn't play well under certain lighting. Had a colleague who simply couldn't get it working in a stage setting.
Doesn't play well for only one spectator.

All in all, definitely worth the money many times over.