Interesting. Not really sure how much mileage there is in an XML representation of MIDI, other than as an implementation detail for bigger packages. I'd venture a guess that 'end-user' adoption is low? In the sense of, for example, people exporting as midi-xml from their sequencer to email to each other?

To be clear, I was more enthused with the collaborative potential and the extremely low barrier to entry, rather than with the notion of a text-file-based representation of sequencing. This project seemed more immediate, hackable, 'tactile' in a way, and more shareable than other formats/tools that I know of; although of course much less powerful.