They are heavy, that was my first impression. My cousin lives on Camp Lejeune so finding one wasn't a big deal. The thing I didn't like was the lack of attachment points on the belt. I HAVE to have that or I will walk. Otherwise they were darn near perfect for taking a beating.
I have one and have used them since the Marine Corps issued them. They are a little heavier than most hunting packs. The material is a little noisy in heavy brush. They are a durable pack and can handle a heavy load as good as any internal framed pack I've worn. I think it carries a heavy load better than eberlestock J series pack. Side pockets and straps are great for attaching a rifle. My biggest complaint was the base weight and noise on limbs or brush. Also I prefer to have a smaller pack after I get to my bivouc. I'm currently using a horn hunter system.
Same conclusion during my search this winter and if I could've handled one might have made a purchase considering the price tag. Bought horn hunter for a backup last fall and now waiting for an MMR frame to come.
I'm in the Corps and am issued one. As far as durability, it can take a beating. Handles 100lb loads pretty well, it just is heavy and has a lot of extra material. But from a Marine's aspect, it is required or these packs would not last long due to the beatings they take. Good durable combat pack, not a good lightweight backpacking pack...in my opinion.