Anything that motivates someone to play and practice can be considered a good teaching aide. I've had some experience with Rocksmith and thought it was cool for the most part - the beginner guitarist will learn how to move across the fretboard, play in proper rhythm and time with the song, and learn how to play simple riffs that eventually become more and more complex as the he or she progresses. The experienced guitar player can use it as a nice practice tool that can provide some challenge and motivation to play songs accurately. The game will not teach the player theory, picking and fretting technique, hand posistioning, improvisation, sight reading, etc. which IMO are all very important for any serious student. So in short, I would say that RS is cool for what it does but it is in no means a substitute for a good instructor.