I bought one for my (adult) daughter and loves it. She leaves hers attached to the fridge, I tried it, but was 'frightened' that I pulled it off and the ball magnets would spring off into outer space... they are that strong that they would probably just stay there!
The ONE thing that takes a bit of getting used to is the fact that the pen itself bends slightly... Normally they are hard, and that is what I am used to.
Fiddling with it is fun, moving it around, and of course spinning it on your finger!