Reading direction should be inverted: we should read pages bottom to top
If I could flip a switch and change this one aspect of modern life, I'd be willing to re-learn all my old reading/writing habits. It just makes more sense to "build" ideas upward.
A problem would be that when writing you'd end up with your arm covering what you've already written and you dont we that problem with the current standard.
Other than this I see no problem with it other than a change to a system that has been the same in many cultures for millenia.