Those who would say it's "easy" should mix things up and try playing it the way it's supposed to be played... while singing!
And the harmonies option makes things hard as well. There are certain parts in some songs where everyone (up to 3 mics) can sing 3 different notes of the same chorus. It's sort of like everyone together is singing a "multi-string chord".
Everyone can and should enjoy this game. It's built on universal properties that everyone enjoys: love, music, and games.