I recently acquired an Arc'teryx Q10 on a special discount from Sierra Trading Post (cost to me with 20 percent discount about $60, o/w presently $76 on sale). This does not have shoulder straps, but a good suspension system with considerable girth adjustability (4"). I've used it on an overnight backpack (I carried a partly filled GoLite Breeze with some light essentials in addition) and several day hikes.
That's not enough use to give any informed opinion on durability (though it appears to have a bombproof construction), but enough to say that I find it comfortable loaded to about ten pounds +/-. The literature says 600 cu -- I measured, and it's 800, approximately.
Towards the mid-afternoon, I find it necessary to readjust the placement every hour or so (a 30-second task) otherwise I get some discomfort (I think a little more fiddling with the suspension would help, or better still, losing a few pounds from my waist). I walked happily for nine hours wearing it yesterday, and I think it is the cat's pyjamas for bushwhacking, as it doesn't catch on branches or low trees. It's also nice to have a dry back in warmer weather.
Hydration-wise, it carries two Nalgenes or 1 L platypus squirt bottles, generally enough water for a day for me. One could combine the lumbar with a hydration pack, I guess, and then be able to just about carry enough for an overnight of tarp camping by using the mesh pockets.
I tried a Mountainsmith lumbar pack a few years ago, but had fairly recently had a back injury, and it hurt to use. It rode differently from this--that was 1100 cu. Nice pack, but it didn't work for me then, and probably would still be problematic today.