I'll start by saying that I've used four camera backpacks so far, including this one. The first was a very basic and inexpensive camera backpack. It didn't have back support and was small in size. The problem was that after using it all day for long walks, I soon started to get severe back pain. So I switched to a smaller, cheaper version with back support, which allowed me to go on long walks without back pain.

I later tried a larger, more expensive backpack from K&F, but it didn't have back support for prolonged use, especially when it was completely full of gear, as it was also larger than the first one I used.

This is currently the best, at least in terms of comfort. Despite its fairly large volume, its lumbar support allows you to distribute the weight across your hips rather than placing it entirely on your shoulders and spine. So, I'd say it's excellent for those who have to travel long distances with a backpack full of gear.

Among the qualities I was looking for in a photography backpack and found in this one are: a breathable back panel with large grooves that allow air to flow, which reduces the problem of a sweaty back (it reduces it but doesn't eliminate it entirely, obviously). The shoulder straps and hip belts are also perforated and well-ventilated, to reduce sweating at the points of contact.
It has a thick, rigid structure that prevents back discomfort from the rigidity of the equipment that can be felt on the back panel. It is rigid on all sides to protect the equipment from impacts.
The straps and shoulder straps are height-adjustable, in addition to the classic cinch straps. It has many pockets throughout, and is made of waterproof material, as well as an additional rain cover.
The zippers are large and sturdy.
The opening is on the back, not the outside, to prevent any attempts to steal gear, although it makes it less convenient to access.
It has a metal frame around the back, increasing rigidity and overall stability.
It has a top pocket that, while not rigid, is still handy for various accessories that aren't prone to breakage or stored in a rigid box.
In short, everything is almost perfect.
The only flaws, in my opinion, are the lack of feet to prevent the backpack from getting dirty when placed on the ground, and the pocket on the back makes it slightly less practical than the classic front pocket, but it does offer greater security and waterproofing. I'd say these are almost negligible issues, and I consider it to be the best backpack I've tried so far, especially because for long journeys with a heavy backpack on your shoulders, comfort is essential to prevent a pleasant experience from turning into back torture (with long-term health problems) and irritation caused by poorly made construction, and perhaps even a sweaty bath from a non-breathable backpack. So for me, it could be an excellent investment.