I'm humping about 45-50 miles per week with 35 lbs. in basically a book backpack. I was getting a good workout but my back and neck were killing me. Bought this pack, put my 35lbs of weight in it and it's been GREAT. The padded waist strap gets the weight up on my hips and off my neck and lower back. The padding on the back has eliminated any back pain as well. No neck or back pain anymore and the hikes are now a pleasure. It's also just the right size to carry on an airplane.
Highly recommend this bag.