Reviving a positively ancient thread now that the second gen model of that pack is out. I've got the 1st gen 40-60L size, and have used it on antelope rifle hunts in NM and WY and a mulie archery hunt in NM. All hunts done while backpacking, carrying food, water, clothes, shelter, and sleep system, totaling 41lbs with consumables, rifle, and optics. Did every animal in two trips, first one with gear and one quarter, offal, and trim meat, second trip with the remaining quarters and head. Pack stays cinched to 40L till it's time to pack meat.
Biggest load was just shy of 70 lbs; not the most comfortable experience, but I've yet to get that much weight on my back and be happy about it. Longest pack out was around 7 miles with the mulie, so 28 miles round with around 1k' elevation each segment. Felt pretty miserable toward the end, but my boots were bothering me more than the pack by far. Longest trip I've ever done with it was 80-some-odd miles in the Sangre de Cristos with a 19lb load and it was crazy comfortable. Plenty of airflow across my back, nice padding on the hipbelt, and the hipbelt pockets are actually usable.
Made a gun holder to secure my rifle to the side of the pack, and my tripod and spotter go on the opposite side in the stretch pocket and secured by the compression straps. I keep my GPS in one of the hip belt pockets, food in the other, rangefinder in the shoulder strap pocket, binos on the opposite shoulder strap held by a Peak Designs Capture Mount, sidearm in a chest holster. The new model has a second shoulder pocket, which I'd probably move my GPS to so I can cram more food in the hip belt. There's also a 60-75L with burlier padding and a stronger frame, which would probably be a better fit for a hunting pack.
You can find the 40-60 for $160 sometimes, which is absolutely bonkers for a sub-3lb pack that can still handle 60+ lbs imo.