When I was preparing for a sheep hunt a few years ago I tried out several packs - 2 used (Old Dana Design and Arcteryx Bora 80) and 2 new ones (Stone Glacier and Seek Outside) -- All packs that typically are praised here and elsewhere.
I tried them all with with as heavy weight as I expected to carry and my favorites were the Dana Design and Seek Outside. I had heard great things about Stone Glacier and wanted it to work well but for my back the others were much better. I ended up taking the Seek outside and it worked great for me.
I guess my point is (as other have said) try out as many as you can and see what your back likes best.
