Temp review (will update as I learn more and more)
This review is coming from someone who is learning his first instrument and from scratch, on a brand new Fender acoustic guitar with the cable. I have the game set to Rhythm Guitar.
In short, the game is definitely good, it will definitely help you learn an instrument in a way that is more fun than having a tutor throwing mass amounts of complicated difficult to remember information at you, but has enough imperfections to make you frustrated and annoyed with each song until you're able to push through them with patience and get used to it. So it might not be better than a tutor, but it's probably not worse either. And it's likely a lot cheaper too... so there's that.
I don't know the game all that well, so I won't pretend to know everything about it, and there's a good chance I might be wrong on a few things I'm about to write, but this is my experiences so far.
I wish the game had better options for setting the difficulty and song speed before starting each song and during the song, instead of a regular speed and instead of the difficulty curve based on how well you do during the song. Because most of the time, I'll finally start to get the hang of the song's current difficulty, but then throw a bunch more new notes at me, overwhelming me with notes I can't handle at all. Most of the time, it'll go from 1 or 2 notes per strum to 5 or 6 in a very awkward hand position on the guitar and quickly go to other notes without even giving you a chance to figure out the first set of new notes. I just end up looking at the screen and going "Are for f****ing kidding me?" and just quit the song and move onto another one that I haven't played yet. Now if I was able to manually set the difficulty myself and maintain that difficulty until I'm ready for the new notes, and if I was able to manually set the speed of each songs, and maybe increase or decrease both while in the song... then I'd probably be a lot less frustrated, would enjoy the game far more and would definitely learn a lot quicker too.
I will add that this is currently the only way that has helped motivate me into learning an instrument. I've tried to self teach myself into learning the piano, drums, etc... I could never learn proper notes on a sheet, let alone get used to the hand positions and hitting the right notes, etc... I can see this game becoming quite fun once I actually start getting pretty good at it. So far, the highest I've reached so far is about 55.9% on 1 song, 50% and lower for the rest, but one of them hurts my fingers a lot (and it tears through finger tip protectors quickly, which isn't good cuz they're expensive) and the the rest seem to get more and more difficult rather quickly.
The game is really good for tuning your instruments (even better / more accurate than the built in guitar tuner), picks up on the notes while playing surprisingly well (unlike Songs2See), it even has options to allow the game to be more lenient on your imperfect / badly timed note playing so even if your instrument isn't tuned in 100% perfect, it'll still pick it up just fine so long as it's set up at a lenient setting.
I do definitely recommend this game since it's currently the best program / game out there for learning how to play an instrument (much better than Songs2See even though S2S might be better for learning the actual notes on a sheet).
On a side note, I do wish the game had a few easy / beginner songs in which rookies could actually complete 100%... like a sort of tutorial, to allow us to get comfortable with this style of game and feel like we accomplished something. Right now, I have a nasty bloody blister on my thumb, I still feel like I completely suck at playing the guitar, I have nothing at all to show my friends for all my efforts, even after almost 20 hours of playtime, I still don't know how to play any of the songs and I have the feeling it's going to require around 100 more hours before I can finally complete 1 song. I have no intentions of quitting, of course, but I just wish the game had a motivational song which we could complete 100% instead of slowly being able to get better over time and maybe someday be able to complete most if not all the songs all of a sudden (since they all feel equally very difficult).