I have been trying to decide whether to purchase RS as a way to share my enjoyment of guitar with my 10 year-old son, so this is a timely question. I see a distinction between learning to play the guitar and learning to play the guitar parts in songs. The former, taken seriously, requires heavy lifting with scales, modes, and rhythmic practice against a metronome, etc and is not an appropriate path for me as a 49 year-old guy. Being able to approximate the guitar parts to songs I love is what moves me and what I want to share with my son, so I have been buying multitrack song cover versions from a karaoke-type site, re-compiling the stems back into an mp3 file in Audacity (minus the guitar part or parts we want to play), loading those into a Digitech GNX4 floor pedal and using the pedal for guitar tones and as a foot-operated backing track player. Just 2 inexpensive Squier bullet strats and two used Digitech GNX4 pedals ,so my son and I are using identical equipment and he doesn't get the idea that Dad sounds better because Dad is using an expensive guitar or a high end guitar effects unit. My son is almost making it all the way through 'Teenage Kicks' by The Undertones and his face lights up when he realizes he is 100% responsible for the guitar sound that he hears when his recorded part is played back to him along with the backing track.
I just learned that RS does not use track stems so you cannot fully mute instrument parts and completely replace the song's guitar parts with your own. .The GNX4 pedal contains an 8-track recorder and I use it to record my guitar part to a track separate from the backing track. To me, the only way you know you are doing it 'right' or authentically is to listen to your recorded guitar part after you are done. So it seems with RS, you don't get much back in exchange for tethering yourself to a computer other than point-scoring or watching graphics go by on the screen.
Also, even with there being over 900 official downloadable songs available, there is so much classic material missing it's not even funny. I understand this is principally about licensing, etc, and UBISOFT's hands are tied if a licensing deal can't be made, so I guess that's that. I guess RS isn't for me and my son. It took me quite a while to arrive at a 'system' that works for us involving creating my own backing tracks from multitrack stems I buy for a couple of bucks each and running them from a floor pedal. It's not perfect - everything is a compromise - but I like it. Plus, if my son decides he wants to play guitar at school talent day, he won't feel naked without RS on a computer. He can just plug his guitar into his GNX4 and the GNX4 into the school's mixing board, step on the pedal to start the backing track and away he goes. Barring nervousness, the 'live' experience is not all that different from a technical point of view from his practice experience. Job done.
If I'm misunderstanding something or missing something reference RS, I'm happy to listen.