Jeffery,
I have been playing Rocksmith for a few months now. I also think that the game has been fun.
The technique games they use for teaching scales, slides, chords, etc are not the greatest tools for learning. For example while playing scale racer you end up crashing your vehicle so quickly you never have a chance to immerse yourself into learning the scales. I found that very frustrating so I started to search for online lessons and stumbled upon Pebber Brown. So far his whole concept of open courseware has been a godsend. So the fact that I am looking for better sources of learning the guitar should tell you about the limitations of Rocksmith as a teaching aid.
I think the best part of Rocksmith is probably the Tone Builder like the other post says. Secondly if you like the songs packs available it's really fun to just play the songs your interested in. Rocksmith drawbacks here are it masks your guitars true sound vs you plugging into a real amp. I play on my real amp to cross check my playing to really hear what I sound like without the computer corrections. Without playing on a real amp I find it difficult to learn what my guitar really sounds like, wouldn't learn how to adjust my guitar volume and tone, and wouldn't learn how to manipulate my amp settings either. Rocksmith simply has you turn your guitar settings to full volume full tone and its computer magic takes care of the rest. It's been a lot of learning so far to play in the real world...
I bought mine online through the PS4 for 19.99. I then purchased a few song packs. The important thing is probably whatever keeps you engaged in picking up the guitar.
Hope that helps,
Twkyle90