It is a performing with other's class. While having not yet taken a formal "one on one" guitar class, i have learned alot from the more seasoned players i've played with, just being exposed to everyone is a huge benefit, as well as getting the theory Dave teaches from time to time.
Having said that, i believe the most recent rating system gives us the motivation to actually use what is taught. I know sometimes i hear what is taught, and don't have much motivation to "step up" and use it. Having not used a taught skill, puts me back to square one, not knowing anything. Or worse, knowing it in my head, and not being able to perform it.
I'll use a Sheriff's training scenario as an example. We train with our firearms by shooting at static targets at various distances. We then qualify with the weapons we carry. We obviously had to learn certain skills to hit the targets. (trigger control, sight alignment, re-load drills, etc.) But bad guys are not paper, and they don't stand still. What motivation is there to use what we learn in a stressful confrontation? Pain! A training scenario involving a bad guy shooting back, with a paintball or airsoft gun of course. Now the person is forced to employ the skills that were taught in a static environment, by using them in a dynamic situation, in my example, an armed confrontation with a bad guy shooting at me.
I can learn certain mechanical concepts, chords, timing, rhythm, etc. But until i get motivated to put them to use, i'll never know what chops i have.