A review by someone who's played guitar for 4 years.
Let's make one thing perfectly clear: Rocksmith does not teach you anything about music. And that's fine, because that is not what it is for. You should consider Rocksmith to be a training supplement and skill-builder tool designed solely for electric guitar. That is what it is and it does that extremely well. It does for electric guitar what Mavis Beacon did for typing when we were all kids in elementary school. It skips a few elementary tips about actually fretting and strumming. I consider these to be vital to new guitarists so I think it's a little odd that they just assume you know what you're doing. It does, however, do a good job explaining all the other techniques.
Rocksmith starts you off very slow and gradually builds up the challenge with its difficulty system. Every song is split into different sections or "phrases" that you "level up" by playing correctly. As you level a phrase up you the composition changes to more accurately reflect the actual fretwork. This both a blessing and a curse. Obviously the lower difficulty helps ease you into the song but at the same time some of the low-difficulty adapations are far too vague to be much help in actually learning the song. I often found I performed songs much better on the maximum difficulty setting because I was more easily able to see the patterns and melody of the song in the notes. Rocksmith thankfully presents an option to manually set a phrase to maximum difficulty.
There are a variety of EXCELLENT mini-games in the "Guitarcade" option of Rocksmith. These present you with simple challenges that quickly become a great way to improve your muscle memory of scales and other sequences. You can practice your techniques with a set goal and motivation to achieve as high a score as possible. This is what makes Rocksmith great; it MOTIVATES you to pick that guitar up and practice with it.
The way Rocksmith distinguishes one note you play from another is, of course, by detecting the pitch from your input. This is what I was most afraid of: shoddy pitch detection, especially on chords and other techniques. Rocksmith pleasantly surprised me in this regard, however. It always read the notes I played correctly. This means you can even adapt songs to your own personal preference and play them your own way so long as they are the same pitch (i.e. the correct notes). Chords play just fine and it can even distinguish whether you're palm muting or not, as well as harmonics.
Rocksmith doesn't punish you for playing when you're not supposed to. I both like and dislike this. It lets you freestyle whatever you want onto songs but it also makes timing (a VITAL skill for any musical instrument) fairly unimportant. You can just strum as fast as you can on a sequence of slow notes and it will be counted as "PERFECT" by the game.
All in all, Rocksmith is an excellent skill builder and guitar trainer. It won't teach you why the "Scale of C Minor" is called the"Scale of C Minor," but it will certainly let you practice it to perfection. Most importantly, though, is how Rocksmith actually motivates you to practice your guitar. It was much more fun for me play Rocksmith's mini-games to practice my scales than when I simply learned them out of a book. I would easily recommend this game for anyone looking to learn a guitar for the first time or any current guitar player who wants a good skill-builder. My only advice: buy a book to go with it!