From my experience, the scoring is sort of consistent. Some rare lines feel weird, like Rensa's "LEFT LEFT-LEFT" most of the times when I press all three LEFTs it gives me a negative. Instead I end up just pressing the first two and that almost always lands me a positive. It's not easy to get A and S, you have to learn the songs, try the different lines, see when you can freestyle and how, and come up with a plan to make points.