I know there is still some work to be done adding code to KISS, but I still find it to be a very fun game to play as it stands. I really like stacking the multiballs with a new song and trying to complete both. Great points to be had, shots are fun to double, and if you want a monster score, you have to be a sniper with every shot (left orbit, Star target area, and right ramp are tough but so satisfying when you nail them). I enjoy the KISS and ARMY hurry-ups (and trying to use the inlane combos), and I hope they add another layer of depth to them (collected x number of each hurryup gives you 2x, 3x, Colossal Bonus).
I'd love to see a 'multikill' type of feature that keeps paying you after you complete songs, as well as a mini wizard mode for completing every song.