Trial and error. Apple = simplifying = one line this year, howabout that? Cuts down on the amount of people in the store, and thus probably the amount of confusion.
Also, I pre-ordered and playing the "i have a 9-5" game too. Feel the pain, just beats standing in line and taking up space/time in there.
I don't think short lines, but less people in the store overall. The amount of people in the pre-order line didn't affect the "buying now" line. I think lines will move quicker because of that though, which is a good thing.
I don't know if it's a UK/US difference, but I ordered from Apple.com, and there was an in-store pickup option. I decided to skip it and have it delivered - but the option was there.