Yep, 3 button chords. All the kids are into it ya know. "Strutter"'s got a bunch of them in the chorus, and I know the STP song (I know it, but I don't feel like typing it out) has some in the opening. I imagine the production team's going to include them in all the songs if they can get away with it. Interesting note on "John the Fisherman" is that Les Claypool actually gave the Red Octane crew the master recording of the song to use. So, you're going to be playing off the actual guitar part and the singer is going to be Claypool, not the studio singer and guitarist.
I still think I'm going to wait until it comes out on the 360. There's a ton of stuff I want to play (KH2, Bully, WH40K Dark Crusade, Mideval 2, FF XII, Gears of War, etc.) that can keep me busy until next year.