I might get shit for saying this but here it goes.... I'd have to disagree about molle cordura type packs from my experience atleast. Got myself the 3 day assault pack, seemed way stronger than any backpack I head. It was awsome cause you could slip out the frame from the inside which was basicly an aluminum sheet. It was very expensive but I saw it as an investment, and I got talked into it, being the modern military version of the ALICE so I've heard. It broke right away, after being on the road for two weeks, of hitch hiking, not train hopping, nothing involving me throwing my pack around or anything ya know, and it broke right away, ripping at all of the seams.And I've stitched it up various times to try tto salvage but any time I put more than a couple of things in there and walk some miles it starts all over again. Damn shame. I don't know, theory of mine was that it mmust of been sitting in some deposit ffor way too long, humidity must of gotten in it, and somehow, rotted the seams, since I have no other explanation.
As far as frame-less packs goes. As much as I dislike carrying extra weight off the rame it's a life saver if you're going to walk a couple of miles or more really with a typical amount of weight. I mean, if you're just doing the carrying a sleeping bag and a tarp I'm sure you can get away with it but usually we end up carrying more than that soo. Anyways. Happy trails.