I have it. As a long time guitar player I can tell you that Rocksmith is a fantastic SUPPLEMENTAL tool for learning guitar. It's chock full of great information for both learning and for reference. It does a fantastic job of breaking songs down and adapting itself to your skill level. It's also a great way for those who might be interested in learning guitar to get their feet wet and see if it's something they want to commit to long term.
Having said that, it will never, ever, ever replace the value of a personal instructor. Anyone who is serious about learning to play guitar should seek out a good teacher to take lessons from. The value in that (along with finding others to play with) can never be replicated by a video game.