While I am a "travel light" photographer, my ThinkTank shoulder bag was putting too much stress on my neck and should area when carrying my gear for long periods. I wanted a smallish backpack to better spread the weight. After a lot of research I came upon this Tarion backpack on sale, and while I wasn't very familiar with the brand it seemed to have most of the features I was looking for.
I've now had this bag for about 3 weeks. While it's described as only a 17L bag, it easily holds everything I typically carried in the ThinkTank shoulder bag (Fuji X-S10 with Tamron 18-300 attached; Fuji 10-34; flash, batteries, mini-tripod; lens filters; assorted small gear) -- and more. It has back access to all gear, plus side access to the camera. The padded shoulder straps are quite comfortable, and the cross halter is useful for keeping the bag positioned properly on the back when bending and turning. The bag is also padded on the side facing your back, which is also the side the opens to the gear for more security.
I like the extra pouch for personal items under the cover flap (which itself has a zippered pouch for smaller items.) My regular sized tripod will stand in the mesh pouch on one side and secured with a clipped strap. I haven't had occasion to check whether the bag is truly waterproof, but the included rain cover increases my confidence everything will remain dry on our upcoming trip to Newfoundland.
The only feature I would have liked to see would be the ability to convert to a sling bag, but I understand that this would likely make the rear-facing gear compartment opening impractical.
So, I am very happy with this Tarion bag so far, and given the apparent build quality, I expect to be satisfied in the longer run as well.