Gee I obviously don't go trekking. I have two Lowepro's. A Magnum AV and a TX 500 and I have had both for ages. I got a back pack and hated it - just because I did - it was fiddly and I was scared my camera would fall out when I opened the back. I got the magnum because it holds a serious amount of kit, and you could sling it over your shoulder to get to a shoot, and it sits nicely in the boot of my car. When walking I take a little kit with a camera and lens, a flash and cards and batteries. Its so totally unobtrusive, so you can take it to social occasions and not look silly. If I do go walk about I am happy to take my little bag. each to their own - serious bush walkers need a good back pack, but if, as some readers might not be, I'd think inside the square (case!).