I've gotten only to play the demo so far. I'm gonna replay it a few more times to get the jist of it a little better. My only legitimate complaint to the gameplay would have to be that the controls. Aside from being pretty stiff some of the mechanics don't play out like a typical action title, but what moves that the demo offered were still easy enough to pull off. I feel I can also get pretty easily accustomed to the driving controls.
What few lines I could get from the demo, I generally liked. Jack Black's still of his own kind of comedy, which to me seems to be of a love-it-or-hate-it category. I personally like him, and I like his lines such as, "Don't tell me I've been slaying hot girls this whole time..."
The artistic direction seems really cool. My love of Rock spreads to just about all the genres of it. I'm hoping there are more landscapes as awesome as the mountain of bones and skulls we started out on.
As soon as I feel the need to take a break from Batman Arkham Asylum (which I bought just a few days ago, granted), I'll probably give this game a look.