Control is one of my biggest concerns with games. If the controls are bad, the game is dead to me. I can overlook bad plot, acting, graphics, audio, and many other things, but I can't overlook bad controls. I have actually played games that otherwise sucked, just because the controls were so awesome.
Imagine your device is sitting face-up on your desk. The acceleration vector is pointing out the back of the screen (gravity). Now if you rotate the device 90 degrees (keeping it face up on your desk), the acceleration vector remains unchanged, pointing out the back of the screen toward the center of the Earth. Edit: it's exactly as if you never moved it. :-)
And as the device approaches this extreme, it becomes more and more difficult to use the 3rd axis to discern exactly what the user "means", especially with a noisy accelerometer.
The general problem is that the accelerometer vector needs to change in order for you to use it for control. And for each of the two tilt types the author shows, it's really easy to come up with a device orientation in which the accelerometer vector remains unchanged regardless of the amount of user tilt.
I mean, something can be done up to a point, but I think "works both ways in any orientation" is going to be tough. There might be a reason why the author has not seen any games do that. :-)
