Like boots, rucksacks are only good if they fit you. Osprey generally has excellent feedback but some people have issues with them being uncomfortable.
They are seen in the hills a lot because of reviews, "fashion" and availability in the shops rather than they are better than anything else. They are excellent, well made packs with some design aspects that don't work for all.
For a large pack as you are buying also consider Gregory who have a good reputation and excellent build quality and I think this year's models all have adjustable hip straps.