This site is a HUGE, constantly growing library of guitar lessons. One thing I love about it is the fact that for less than $15 a month, I can access thousands of great lessons, download them and practice whenever I please. I've tried most of the 'popular' guitar-learning infoproducts out there, and this site, by far, provides the best value for my money (you think it ranks no. 1 for "guitar lessons" on Google by accident?!).
Then again, the site does throw all these lessons in your face with no sense of continuity, or even a roadmap whatsoever to tell you where to go from where. What this can do is (as in my case) overwhelm you, and force you to put off sorting through all the material, and picking a "good" lesson to practice with, for another day. Days become weeks become months and you're still stuck with that Blues Primer 3 tutorial and some intermediate lessons that you dl'd two months ago.
I'd definitely recommend that you join the site as a full access member but only if you're really passionate about constantly finding new and challenging lessons to play. The fundamentals, music theory etc are all very good but can be found elsewhere too. The real highlight of the GT library is the sheer amount of practice you can give yourself.
At best, this site is a collection of superb, professional guitar lessons put together by real masters. At worst, though, it's a random assortment of licks, riffs etc that I wouldn't recommend to my 11-yr old nephew (if I had one) who needs to be walked through every single step of the learning process.
If you're jailed in a real library for one year with a guitar, and you find guitar lessons everywhere you look, would you make the most of that? Would come out slinging your gat, a maestro of the instrument? Or would you come out whining about how the air conditioner stopped working four months ago? If the former feels like you, join right now; you've found paradise.