You know what, I've got to admit that this is pretty good! Overall 'feel' of the menus is perfect, concept is refreshing and executed well (it's casual enough that you could play it with one hand and without focusing too hard, which is good design considering the context :p I like how you can see the colors of the beats even when they're in your peripheral vision), and the mod support just completely elevates it above and beyond since its so easy to make a mod for your game (at least from what I've seen at the wiki).
You've done a wonderful job with this, keep it up!