I bought the one offered by NatGeo's Joe Sartore and found it to be good and inspirational. It was around five or six CD's long. Over all it was a good course and you can watch at your leisure and over again if you like.
Just thinking, I should get my order together and sell it, I may try to do that sometime.
The worst part of the deal is if you order it, you will get a great courses flier every two days for the rest of your life. You can't get them off your back wanting you to buy more and more. You can't burn them fast enough, they will cut down a forest to make the paper to keep sending you fliers. I got so sick of them that I swore I would never crack open another flier from those people.