Rocksmith is not perfect, but it is great.
The pluses are so big and obvious that the minuses are outshined.

+ will help you get you started with a real guitar
+ is fun to play
+ provides a sense of reward over and over again as you progress

- it could be a little more accurate (sometimes if you play the right notes fast in a row it gives you the "green light" even if you mix up the order
- it does show you the key technices but it can not give you any feedback about your technique when you apply them
- it does not have an A-B-C type of progression aside from sorting songs accroding to difficulty that also seems a little wonky
- the interface is a little slow

Rocksmith is the type of game where the more you put in, the more you get out. So be sure to put in plenty :)