One aspect that bugs me with this game are the voices in the tutorial section. This is probably because I only have the german version of it (I actually think it is a multilanguage version, but I'd probably have to change the language of my Wii console and I can't be bothered to do that), but it made me already feel extremely idiotic standing there with the guitar just listening to a voice that trys too hard to be funny. And everytime I show the game to someone, he or she plays the tutorial and I have to hear that voice again. Soon it will haunt me in my dreams.
Other than that, it's my first Guitar Hero and I like it, although I will probably never ever finish the game on hard (let alone expert), the last few songs are just too hard for me (managed Cliffs of Dover, but thats about it). However, given the feedback here, I suppose the predecessors must have been much better - I should try to convince my PS2-owning sister to buy these games then! I'm trying to convince her to buy Rock Band once that comes out here already, maybe that induces the rhythm-game-love.
The star rating... It's probably just the amount of notes hit, while the score also takes the "when" you get them into account, as it resets the multiplier (i.e. if you make all mistakes at once, you only have one section where you messed up your combo, while many mistakes all over the place will change that).