I am a devotee of Peak Design, who make photography bags that can be used for everyday use as well (hence the name of the 'Everyday' line they put out). I use their Everyday Messenger as my primary work-bag, and I've put it through hell for nearly 3 years without any significant damage to it. They also have an Everyday Tote I adore.
Now, I do not own the Everyday Backpack, but I've heard excellent reviews of it, and based on the durability and comfort of my other Everyday bags, I feel confident recommending it.
The downside is that the Everyday bags are not cheap by any measurement. But again, I've put my Everyday Messenger through hell—rain, mud, daily bus rides, dumping it onto the floor at the office, etc.—for going on three years, which is far longer than any other bag I've owned has ever survived. No broken straps, no broken seams, no broken zippers or snaps.