This lens, mounted to a 5DIII, is the mirrorless / Leica X2 / Fuju X100 killer that everybody's been dreaming about. It's got all the photographic goodness everybody keeps saying they want in a compact body and then a whole hell of a lot more, and the combo is hardly bigger than a compact. It's eminently pocketable (in a way that a 5DIII with the Plastic Fantastic isn't), and non-photographers will look at it and only see a high-end P&S -- especially if you shoot with Live View at arm's length.You're stretching the truth with the bolded parts. For starters, this thing is only 3/4" smaller than the 50mm, its negligible as a combo. Especially when you consider that even my rain jacket pockets would struggle to fit my 60D, and that's smaller than the 5dIII. Nobody is gonna confuse a 5dIII for a P+S. An NEX with a pancake is pocketable, but it's literally half the height and depth.
I agree that this would be a great combo as a prime, but lets not make it the game-changer that it isn't.