Amazing game, it has a nice look, a really nice sound and is very fun to play. I loved being able to select my next upgrade, made me stop mid-game and strategize over which one would be the most effective for me. I also loved the final boss, was a really cool challenge dodging it and its minion flamethrowers/bombs.
My one complaint is that the game does not seem to punish you for just mindlessly spam clicking, which seems a bit counter-intuitive for a rhythm game. Would not mind some sort of a penalty for trying to shoot out of line to force the player to actually learn the rhythm. Other than that, very nice. :)