I just beat Ouendan on Hard mode...and, yes, Ready Steady Go is easier on Hard than Normal...or maybe I've just gotten much better. Whatever.
But, HOLY CRAP, Insane mode is hard...all the hit markers are smaller and further apart from each other, so they're harder to spot...plus they show up later, so you pretty much have to KNOW where they are. You can't just find them.
I should probably put this on GameJar, but I don't feel like updating that, and I don't think anyone clicks there anyway.