I can beat the 1st 3 or 4 groups of songs on expert, but barely. Once I get into the last 2 or 3 groups on hard though I start having a lot of trouble. Fucking Cherub Music beat me down for a little while too on hard, those 3 note-chords are tough when you 1st start doing them.
And Lou is actually pretty tough on medium. It really depends what power-ups you get too.