I don't have a "camera" bag, simply because for me the situations never demand one:
-Going "for photos" around the city or nearby: I carry the camera on its belt strap and, if needed, a couple extra lenses in a small sling pouch (generic 10€ polyester bag my parents got me for school trips when I was like 12). In winter, the lenses might just go in the jacket pockets
-Meeting someone or I don't feel like using the belt: camera with hand strap in aforementioned bag. The K-1 fits snugly with a smallish prime mounted.
-When hiking or traveling, I want a proper backpack so I carry my Osprey Talon 33 with food, drink and the extra lenses/tripod. Fits like a glove and carries everything.
I understand the appeal of specific camera bags, but I've found that for the situations I find myself in they aren't really useful. The belt clip's the best invention there IMO.