If you were wondering what the native SDK would open up on the PlayBook you now have another answer. First Drodin ported the classic Linux game, Extreme Tux Racer, to the PlayBook. Now he has continued with NeverBall which is another open source GPL 3D game. The game essentially has you controlling the ball with the PlayBook accelerometer and swiping for menus. All in all it is a pretty solid clone of games like Marble Madness and Super Monkey Ball.
You can pick up Neverball in App World for $0.99 or download it on your PC free