In my opinion, the greatest weakness of traditional music notation is that a same melody has to be written in 12 different ways, depending on in which key it is. After you've trained yourself to read in all 12 keys (or 5-6 most common ones), everything works nicely, but that's a lot of repetition.

A notation that would solve this problem, would be great progress.

But this Hummingbird notation does nothing to help with this problem.