Neil,
IMO, part of the problem with most training agencies, is they instill absolutely horrible diving practices right from the beginning and do little to curve it as students progress. IMO, good diving form and philosohy are just as important as the material being taught. GUE has much higher standards for acceptance and graduation.
You say that IF you are teaching gear configuration and philosophy and nitrox, then it's not really a nitrox course, but I say it's still a NAUI course. Those students represent Naui and Naui instructors. When I see students being rushed through courses with the prime motive being money, it leaves a very bad taste in my mouth. When I go on a charter and see 50% of the divers asking how to put their first stage on correctly, it leaves a very bad taste in my mouth. And when I'm under water with these "experienced" divers and see octo's and PG's flying all over, horrible buoyancy control, OOA situations, it leaves a very bad taste in my mouth. I see this all the time, but especially in the tropics. Do I blame the agencies? For the most part. Not trying to start a war here, but am giving a word of caution to the unsuspecting.
As far as George Irvine, he's not an instructor. In fact, I believe he only has two or three certs of any kind, but he knows more about real decompression and physiology than nearly anyone in the sport of diving. Does he know anything you or I (or anyone else) can't learn? Nope. In fact, he's opened his brain to all those interested in learning -- for free.
Take care,
Mike