my son loves the lego games (batman, indiana jones, star wars). pretty much like regular games except the scenery explodes into lego coins to be collected.
what most of the commenters on that link fail to realize is that this game will not be marketed towards them. it's gonna be for kids. my son right now could care less about regular rockband. but you slap lego on it, and make it easier, and he'll be all over it. probably let them be more involved with set designs and stuff too I would imagine.