Not sure it needs to be this small
I can certainly see that on some people a much bigger bag would be a problem in how it hangs or just looking kinda funny. the thing I like about the Buzz is the single strap - I have never used two straps and I hate all the extra strapping hanging off bags. Looks like a silly octopus hanging from someone's back. That's why I love the Buzz style - I even cut off the hanging extra strap so it is very minimalist.
However, it barely fits a 12" PowerBook and when I keep the laptop in a protective padding case (I usually cary it in a RadTech casing) it won't even fit in the bag. And the 12" PB is about as small of a laptop as you're going to find.
I'm 6'2" and could certainly have another 3.5 inches in height on this bag, maybe another inch of width and depth too. Granted, it may not look as cool as the current size on a smaller person, but it would be immensely useful in so many more cases. I find myself unable to use the Buzz for anything but my light commute days to and from the office because I can't even put a manual in the bag with my laptop.
I personally would just like to see a single-strap, simple bag (like the buzz) that can hold a 15" PowerBook, a bag of power cables, and a book. The single strap that rids on the back (not the hip) is the key.