i have the first rocksmith game for the xb360. pretty awesome game. i've played a bit of guitar here and there. mostly self-taught and using tabs. the only problem i have with it was that the learning curve was pretty quick within the game. the game itself changes based on your skill level, and will either increase or decrease in difficulty (accuracy) mid-game unlike rockband or guitar hero. so the song might start off with you just playing one note (instead of chords). then as you keep playing, and are more accurate, the one note will turn into two notes or into a full chords.
so you start playing for a while with normal power chords... then some more complicated chords start popping up... then some chords i've never seen before. i have no idea how to get those right, and then it bumps the difficulty level down sometimes back down to one note again.
there are also mini games that help with "skills" such as slides, chords, picking techniques, etc.
overall, i think it's a pretty fun way to start learning how to play the guitar, but it's no replacement for a true instructor.
that being said, i'm interested in picking up the new one. i'm sure they've worked out a lot of issues with the first game, plus added songs are always nice.
another cool plus is that the cable is universal (to the best of my knowledge). i can use the plug to plug my guitar into my mac and use garage band to record stuff.