After the severe back pain I experienced at the Lock 4 six-hour race a few months ago, I decided to try a Wingnut pack (specifically, the Splitback model). They’re designed to sit lower on your back, distributing the weight of the pack across your hips rather than up on your shoulders.
First off, you are going to pay more for one of these packs than you will for a traditional “camelback” style pack. They also don’t include a bladder.
However, after just a few uses, the cost has been more than justified with me. I’ve been on multiple 4+ hour rides since I purchased it, and I haven’t experienced any back pain (I’d originally thought that bike fit/saddle/general fitness might have had something to do with my pain, but apparently not). The construction is excellent- it’s lighter than most packs, but handling it, you get the sense that it will last forever. My favorite part is the side pockets- they’re roomy and really easy to get to while you’re riding (I even manage to get to fish stuff out while wearing heavy winter gloves).
The capacity of the Splitback is excellent- it can easily hold a 100oz bladder and whatever else you want to pack in- when I’m out for a long time on the trail alone, I usually carry food, a small camera, phone, folding saw, extra gloves, multi-tool, emergency blanket, lighter, pocketknife, waterproof shell (if rain is in the forecast) and still have room to stash a layer or two if I remove one while I’m out riding. Unlike some other packs that can hold this much (530 cubic inches), the Splitback only weighs 13oz. Salomon makes a comparable one (weight/cost wise) that’s slightly larger but doesn’t feature the “lowrider” system of the Splitback.
I know I sound like a total shill here, but with the humongous improvement I’ve had in my ability to ride for hours without pain, I can honestly say that this is one of the best (if not the best) pack available.