Kbarkamian, I'm with Unsound on this one.
I've watched people play it and I just walk away. It might be a game, which I understand, but hitting buttons and pretending to strum or drum? Maybe I'm just too much of a prude. Maybe it's because I've put so much time into getting to the level I'm at with the instruments I do play (violin for nearly 18 years now and drums for about 14 years) that it just feels like a mockery to downgrade it with a game that merely pretends to play. Either way I still can't even picture myself ever doing it.
And absolutely nothing against those that do play it. If you are entertained by it then great. That's what it's about. And if it exposes people to new music, even better! And if it gets people into playing real instruments then I'm even more thrilled.