Being used to Rock Band...
I didn't quite like this game. Not only are the fret runners hard to see (the screen is both dim and small - and no it's not just my TV), the timing of the game for the guitar is incomprehensibly hard to get. My friends and I "just can't get it". Plus, the choosing of difficulty and bass/guitar comes before the game, not before each song.
That said, the bar style for the vocals is a lot easier to manage than Rock Band's, and the range of songs is more varied - which some prefer as a change of pace. One of my friends who's a jazz drummer loves the funk songs available.
I'd give it 3.5 stars - it's a good game but being used to the Rock Band franchise, I cannot be but slightly biased against it.