As others have said, this game is not a replacement for a human guitar teacher. The advantage here is that you get to jump in and start playing songs right away, and let's face it, that's the reason alot of folks give up on their "regular" lessons early on. Nobody wants to spend five days learing how to tune their guitar even though they should. Nobody wants to spend another fifteen days learning how to play "Mary Had a Little Lamb" even though they should. People want to pick up the guitar and play "Sunshine of Your Love" in ten minutes, and Rocksmith lets you do that... sorta.
Rocksmith won't teach you to play any song you want on the guitar in a week's time, but what it does is get you used to holding the instrument and what to do with your hands. The first time I ever played Guitar Hero, I think I might have hit a total of ten notes in the song. But eventually my left hand learned which button was which and how far apart they're spaced, to where now I can play alot of songs on 'expert' without looking at the controller. Same concept here. Within about an hour my left hand learned how far apart the third and fifth fret were and I could transition between the two with a fair amount of success without looking at the guitar. If you want to learn the guitar, Rocksmith is a great jumping-off point. Play around with it, get familiar with the instrument, then take some professional lessons or buy the self-instructional DVD's if you want to learn the nuts and bolts of what it is you're actually doing. If you don't want to take it that far, play the game for a few months and impress your friends next time you go over to their house by picking up that old acoustic guitar sitting in the corner and busting out some Nirvana Unplugged for them.
Long story short: I bought a guitar, I bought the books, and I bought the DVD's. Nothing was more boring or frustrating than sitting in my living room by myself with a book open in front of me or a DVD playing, trying to teach myself the guitar. I learned nothing. Rocksmith is fun... end of story. If I learn to play the guitar when it's all said and done then great! If not, it's still a ton of fun. Analyzing the reviews out there and most importantly who wrote them should help you make your decision. Gamers are rating it low and musicians are rating it high, that should tell you exactly what you need to know. I'm not saying one group is right and one is wrong, just that one is viewing it as a "video game" like Guitar Hero or Call of Duty, and one is viewing it as an interactive instructional tool for beginners and/or a fun diversion for professionals. If you're a gamer looking for a game, pass. It's too expensive and there aren't any guys with funny accents for you to blow away with an M16 or quests for dragon's balls. If you're a guitarist or a wannabe guitarist who also happens to own a video game console, it's a must buy.
** UPDATE ** Now that I've had and played the game for a week or two, I'd like to expand on my review a bit.
Before I bought Rocksmith I could not play the guitar. I mean it, I could not play a single chord or make any sound that resembled any part of any song in the known universe. Now I can play through "In Bloom" and "Sweet Home Alabama" with relative success every time. Herein lies both the benefit and the drawback of Rocksmith. Yes, I can play both of those songs I mentioned (among others) as long as I'm playing along with the game, but I haven't truly learned the songs. I don't know what notes I'm playing and I cannot apply what I know about playing "In Bloom" to any song not in the game.
When a human guitar teacher teaches you, you learn that placing your left hand here and strumming the string(s) like this is called G-sharp, or E-flat, or the G-chord or whatever. Rocksmith simply shows you that putting your left hand here during "In Bloom" and strumming these strings with your right hand during "In Bloom" will make the proper sound for that part of "In Bloom." I haven't truly learned what it means to play those notes, only how to play them. I don't see how the lessons learned would transfer into being able to read, play or understand any song not in the game.
That said, am I changing my review or my recommendation? Absolutely not! I stand by what I said originally: Rocksmith shows you how to hold the guitar, where to place your hands, and how to play notes. It allows you to play songs right away without trudging through days/months/weeks of music theory or just playing one chord over and over until your fingers bleed. If you want to know the "nuts and bolts" behind why when you place your left hand here and strum with your right hand there it makes the sound it makes, buy some instructional books or hire a human teacher. I guarantee you'll be a step ahead of where you would have after playing Rocksmith than you would if you hadn't.
The only thing I feel really needs improvement before Rocksmith 2 comes out is the on-the-fly difficulty needs more fine tuning. For example, after playing "In Bloom" on what was surely the lowest setting the game offers, I felt like I was getting the hang of it and wanted more notes to come at me. It took a while before it thought I was worthy of more notes but when it finally did, it threw them at me fast and a-plenty! Only after failing miserably two or three times in a row did it slow it back down for me, but even then it slowed it down too much. Finally it hit a happy medium with me and I felt comfortable with the pace, but that was after playing the song through four or five times either too slow or too fast. It's a great concept and amazing technology but it has much room for improvement.
Overall I stand firmly behind my day-one review. Rocksmith may not be the best teacher in the world, but it's a helluva fun game and it took this guy - somebody who'd barely even held a guitar - and turned him somebody who can actually play the guitar... to a certain extent. But I am getting better!
** UPDATE FOR MY UPDATE **
This game's been out for about a month now and I can say I have some serious time into it. It's still fun and I still like it, but I'm demoting it from my original 5-star review to 4-stars based on some shortcomings I can't ignore. I know my review's already so long most people haven't even read it, so I'll keep this short lol!
1) The adaptive difficulty feature needs some serious refinement. I touched on this earlier, but it switches between "Eric Clapton Mode" and "Chimp Holding a Guitar Mode" too often and never at the right times. When I start to ge the hang of a song, it triples the single notes and throws all the chords at me at once. When I screw that up as I invariably do, it takes me back down to what must be the lowest possible level and it throws me off.
2) There should be a section where you can practice chords as long as you want. As it is now, you can play these short little songs consisting of a few chords repeated, but once you've finished the song you're done. The mini-game "Dawn of the ChorDead" is (or should I say "could be") awesome, but they should let you turn off the scoring and just play as long as you want. It's alot of fun and I felt like I was learning, but when you get eaten by the zombies you have to start all over again. Which leads me to one of my biggest gripes...
3) LOAD TIMES! They're inexcusably loooong and are honestly ruining the entire experience for me. I'm a beginner. I never played or barely even held a guitar before this game came out. I need a section where I can just practice chords, hammer-ons, pull-offs, and all that other stuff over and over again until my fingers bleed. Sure, there are a couple different sections where you can practice all those techniques now... for a few minutes, then you have sit through a load screen for feels like an eternity if you want to do it again. If I could play the Riff Repeater 100 times in a row like I want and not 5 times like it makes you, or I could play "Dawn of the ChorDead" for as long as I want and not only until I miss 2 or 3 chords and get eaten by the zombies, then the load times wouldn't be an issue to me whatsoever.
I still like this game and I still play it often, but it's not perfect. Hopefully Rocksmith 2 will have the necessary improvements.