Do you need to GTD?
Do you need to "do" gtd?
Part of putting this information out to the masses makes it necessary to "generalize."
If you're getting things done, not dropping balls, and making productive use of small windows of time (so you can get on to what you want to do) then don't change!
For the most part, the people who are drawn to this stuff are those looking to shave "time" off of their work-day. For example, sitting next to a man on the plane recently, I noticed a two-fingered, hunt and peck typing method in place. (Now, this is not "only" GTD material...)
I could only wonder, "If he typed at 30 words a minute, would he be able to leave the office a half hour earlier?"
NOW, some people don't WANT to leave the office earlier! Others, like Tiger Woods looking for that next level of his golf game, are looking for the one computer shortcut, or the one filing system, that one idea that will make their day easier.
So, bottom line to all of this: Do what works to keep you going. For folks who don't miss-agree (say they'll do something and then "forget"), for folks who talk positively to themselves, for people who are already "there" whereever there is, this course is going to be a nice, icing on the cake.
For others, the ideas presented here are going to be radical solutions to their most pressing problems.
I'm drafting an essay for our website. It's called "Small Windows of Time." I've had too many people call us and say, "Using GTD, I can now take advantage of the small windows of time. This encourages me, gives me more energy, and lets me get home earlier in the day."