First things first: this bag is huge. It certainly fits the bill as a 3-day bag, which is precisely why I bought it. There is enough room for a change of clothes, or 2, along with other gear for an unexpected stay away from home.
The nylon feels very durable and thick while not being too terribly heavy. I have a daily-carry bag that is 1050-Denier nylon and this bag feels a bit thinner, maybe around 800d to 900d. Still plenty durable. It has 3 grab handles (1 top, 1 each side) making it very easy to get hold of the bag from a trunk, toolbox, back seat, etc. I've not made use of the water bladder pockets but they seem well-thought-out. There are ports on either side of the top grab handle for the drinking tube so you can place it on whichever side is convenient.
The shoulder straps are well-padded and come with nylon webbing running down them providing attachment points for all kinds of gear as well as drink tube routing, along with a very small but serviceable sternum strap. The waist belt is similarly padded and can be tucked back into the sleeve to keep it out of the way. I've not tried removing it but it feels like it's just velcroed into the sleeve on the back of the bag, so it likely can be removed if desired. The waist belt has no webbing for gear attachment as the belt design would interfere with the webbing. A slight redesign to make the waist belt more like a 'battle belt' would be a good idea, but it's perfectly serviceable as is.
The main compartment is huge, with 4 straps (2 horizontal and 2 vertical) to tie down the contents and keep them from shifting. I currently have 1 change of clothes in there and there is still plenty of room for more stuff. The two small side compartments serve as general purpose pouches. I have my fire-kit pouch in one and a folding e-tool in the other. I could still fit more, even with those in there. The large bottom pouch serves me as an excellent tool compartment. 3 elastic-topped mesh pouches store a few Clif bars, while the main zipper pouch holds a paracord spool and a pair of leather gloves. A large 6" fixed blade just sits in there.
The upper compartments have yet to see any real use, but they're there. The admin compartment has ample organization for notebooks, pens and the like, though I like to keep all my writing gear in a separate, smaller pouch. It also has 2 shock-corded pouches sized for AR magazines, as well as 2 larger full-width document sleeves. The rearmost is full-depth, while the fore is about half-depth. The nylon in this admin compartment is much, much thinner so I would avoid putting anything in there with sharp corners or stuffing the sleeves too full. I carry an aluminum form-holder in a neoprene laptop sleeve because of that.
The exterior webbing is plenty sufficient to attach whatever one might need: I currently have a first aid kit attached for emergencies.
I've had the bag for several months but have not put it through any real durability tests, but it seems like it will hold up quite well. Considering the price of equivalent alternatives, this bag is a considerable bargain.