I play song difficulty up to only around 15. Not that much of a
problem, for now. For me, at strenuous parts of the songs that
require multi buttons i just press the keys faster than what it
should be.
And if you didn't know, setting the keys to "Q,W,E, spacebar,
I,O,P" will smoothen it out slightly better. Pressing up to 6 keys
it will 'jam'.
But it is still better than the default setting where you 'jam' at
4 buttons.