Super-addictive.
The rundown:
The premise is so simple, tilt the level the control the monkey and ball and maintain enough momentum to reach the goal without flying off of the edge. Sounds easy, no? It is, at least for the first half of the game. At about the mid-point of the Advance stages, the difficulty ramps up to the point of unfairness. You just want to crack the controller and smash the tiny bits into your eyes. But the sheer fun keeps you playing, at least to beat "just one more level". My main complaint is the annoying sound and the slightly gay level announcer.
A game for those with incredible patience, this game will go down with the greats.