I checked this out on the N900... Here are my thoughts:
- keyboard panning is a good idea, but the offset seems arbitrary, and also far too small to be useful (where useful means >= as fast as using the pan button). My suggestion would be to have it pan vertically by lines (when on lined paper), and something more sensible horizontally (e.g. maybe the length of an average word or two). Also, I would recommend mapping wasd to the same functions (for left/right-handed use), and making right/d at the edge of the page act as carriage return (and possibly left/a at the left edge do the opposite?).
I think this would be more usable than just incremental panning with the arrow keys, as it would allow the user to page forward/backward/newline with one hand while writing with the other. This would also completely satisfy my request for something of this sort from earlier in this thread.

Does this sound doable?