When I first saw the Urban Disguise bag I wondered how the heck such a narrow bag would work in the real world ... but I ordered a 40 anyway to see first hand.
(Mainly as a supplement that can slide over a roller bag handle without hanging out as far as a conventional shoulder bag.)
Well, it's amazing ... the UD40 shown below is holding a Nikon D-3, D700, SB900, SB800, 14-24/2.8, 24-70/2.8, AFS50/14, 85/1.4, 2 different flash diffusers, and a wallet full of CF cards.
It's like a VW Bug with 1000 clowns pouring out of it.
My only complaint is the strap inside the cover is very, very difficult to open ... which makes you wonder if anyone actually tried it before selling it.
I used a Nikon 100 macro + 1.4X next to the bag for scale.