Arc'Teryx Quiver Pack
I've admittedly never taken this into the backcountry, but I use it for a daypack and for my SLR camera. I've found that the camera, one other lens, a rain jacket, and a bit of food fit in there perfectly. There are two pockets, one on the outside that's the perfect size for film or your extra CF cards, and one large compartment for everything else. There's also room for a hydration bladder and a port for the hose. The 3-point design makes for quick access to your accessories without having to take the pack off. It's also waterproof and rather slick looking.