Accelerometer would shine how? How would it know how much tilt the user gives means how much interface should be changed?

The power of N900 lies in touch screen with keyboard IMO. That Apple monster has only 3 hardware buttons (power, volume_up, volume_down) and there is not much to control via that.

I know what Fruity Loops is, but TS made screenshots of the features he needed. I don't see any screenshots of software synths. A sample player it is, and it can resample, but I'm not aware it has (software) instruments you can record, although it does have MIDI support.