Bagwards Thinking: Using your bag as a constraint on the things you get/use, instead of the reverse.
So, my previous laptop was, an 11" MacBook Air. One of the criteria for getting it was: It must fit in the bag I am using.
Well.. that bag died, and I got an Empire Builder. So now the 11" Air was small for the bag, a friend happened to make a good offer to me on it...
Turns out a Retina MacBook Pro fits quite well, in the EB, though I do remember feeling a bit sheepish as I grabbed on of the Apple Store rMBPs and tested that it fit. Can't really get a laptop that won't fit the primary bag you are going to carry it in!
My thinking was/is: I carry the same size bag regardless. I might as well get the laptop I want inside it... No use in "wasting space" :)
(And the rMBP is about the same thickness as the air.. so not much space lost... a bit above the air, but I'll live, really.)
Any other "bagwards" thinking people have shown?