I have been quite happy with my Lowepro Nature Trekker AW. I have had it for about three years and it has held up quite well. It is large enough to hold my entire Hasselblad system (body, WLF, two backs, three lenses with hoods not attached, PM90 prism, filters, Sekonic light meter, Vivitar 285HV and two extension tubes). I also bought the daypack for it, which attaches nicely to the front of the bag for extra clothing and snacks.
I have used this for medium distance hikes (8 to 12 miles) and it has been very comfortable. It also does not have that "camera bag look" and it is small enough to take on a plane as carry on luggage.