I decided to go Full Access after all and have some comments on this progress bar.
First of all I agree with almost everything adir olf has to say, and I would like to add my own suggestions with it.
My suggestion would be to combine it with the bookmarking thing and make it into a "progress overview" (eventually ereasing the bookmarking, making this progress overview replacing the bookmarking) that you can manually maintain. So you can add lessons to this page and slide the progress bar yourself, not GT doing it for you. It would also be nice to have a small field where you can add some notes for yourself as a reminder. For example the Hotel California lesson is huge and I would be able to add a note: Return at video 5 at 4:25 in the video. Those sort of things.
But it would be awesome on the overview page if I can look which lessons I'm currently working on (which I currently can't except when I visit the lesson). Perhaps even archive a lesson which you most likely won't visit anymore so you can keep the overview nice and clean, but still have marked lessons as done.
This way I think everyone will get a much better idea what they still need to work on without getting confused. And I'm sorry to say so, but I got this idea from your main competitors (not going to say their name). They've also got this integrated the way I describe it here and it works brilliantly.
Hopefully GT can take this into consideration.