There was a time when I was maxing out with two laptops (Thinkpad 14", MBP 13") in the (detachable) vertical pockets, a Canon 5D mkII, a single 24-70mm lens, and some misc items.
Handle straps are long enough that you can swing the bag to your backside and keep it there, rather than hold it to your side like you would a typical tote. To fix in this position, you can undo one end of the stabilizer strap and loop around the handles and buckle (E demonstrates this in a release video). OR you can lengthen the stabilizer strap in it's 'stationary' location to match the length of the handles, flip the bag on its side and use as a backpack. Of course, not a true replacement for a backpack, but it functions as one when I need it to.