I've always carried a shoulder bag, because the gear is right there at my fingertips, horizontal to the ground, I can just rip open the top grab my current setup or very quickly switch a lens. But, I do multi-hour hikes to locations all the time, and the fact is, the shoulder bag is hard on the body. I think about switching to a backpack ALL the time, but every time I go down to the camera shop and have a look, I just can't get over how clunky and inconvenient a backpack is. So my question is, are there any backpacks out there that might satisfy my need for speed and versatility? I carry a 1Ds Mk III, 5D Mk II, macro lens, wide angle lens, flash and 28-70mm zoom. But I'll want a bit of extra space probably, because I usually would carry some snacks and odds and ends in a day pack along with my camera gear. '