OK, so as of now, I'm on a trial account, and I'm questioning how useful this site is for what I want to learn. As a guitarist, I'd say I'm 'proficient' at best. I'm able to learn and play fairly complex songs (Hendrix, SRV, Zeppelin... etc...) but learning and playing someone else's work is NOT what I want to do.''

Now, I can easily make up chord progressions, solos, and the like based on songs I've heard and songs I've learned, but I don't know WHY certain patterns fit well with one chord progression, badly with another, and just sound so-so with another.

The sample lessons included in the trial account include VERY little on theory beyond - this is pattern X, it fits with progression Y. So I guess my overarching question here is this: How well does this site cover music theory? And I don't just mean basics. I want the what, the how, and most importantly the WHY of all this. I don't want to spend 10$ to find out that this site doesn't have what I want, but I also don't want to shell out 60$ for another month of guitar lessons if I could get the same for so much less.