Maybe the subtle difference is that with a straight you automatically reduce the angle after the first pass because you see so much more of the blade. In the very few times so far that I've used the DE, I noticed that I don't have the same feel for the angle, therefore it makes sense to turn it down a notch or two via the adjuster - I guess this doesn't really add much to the overall shaving time. The point I was trying to make originally is that a very simple idea had not occured to me before.

Edit - this was intended as a response to BobH above.