They have to market it as a "game" to get that demographic that was into Guitar Hero and Rock Band. But underneath the hood, this is straight up a teaching tool first and then a "karaoke" machine 2nd as a center piece for you and your friends when they come over. Yes, they have Career mode in Rocksmith which basically has you traveling all over the world, starting out in small venues to play in bars and whatnot. You have set list that you perform and every song, every venue, everything that you do unlocks more and more leading your way to playing Arenas and then eventually Stadium shows. That's the "game" aspect of it. The rest as they say....is gravy.
The note highway does take a bit of getting use to, but it's not as hard or as complicated as it looks. Most of the stuff they show in the video is usually Master Mode, so you see all these notes flying at you super fast and it came look daunting. The thing about that though is that you can manually set the difficulty level to your liking. The lower the difficulty, the few the notes you will see coming at you and vice versa.
For existing guitar players like myself, the best thing about this is that we are basically getting our own in-house band with access to tons of songs that otherwise would never get the chance to be played if you don't have a band on hand to jam with you.