I'm glad you liked the song, it was a blast to make! :)
Decreasing the velocity of the green notes is a good idea. After playing it a few times since the submission deadline I've realized that I think the player moves way too slowly as well, and when editing is enabled again I'll probably upload an update with a greater player velocity (if it feels like an improvement when play testing). These two fixes should help mitigate the issue.
Being repetitive is also something I'll try to do something about. I have some ideas that don't break the piano concept, but I had to balance making the game with university, so I didn't have the time to make anything too advanced.
Thanks for the feedback, and thanks for playing! :D