Alpkit Gourdon 20. Cheap, waterproof, holds stuff. What more do you need for riding to work?
It’s just a bag with space inside, a single compartment. For commuting on a daily basis, I’d want a seperate compartment for tools, pump, spare tubes etc. I don’t want to have to pull out a load of clothes and lunch just to get to a multi tool that’s sunk to the bottom of the bag – especially if it’s raining. It also looks like it will sit close to every inch of your back and not let air between your back and the bag so sweat galore.
I’ve been using an 20l Osprey Syncro for a few years now with the cage to keep the bag off your back and allow air through. Quite happy with it, though would prefer if the straps over the chest allowed more airflow through in the summer. The mesh to keep the bag away from your back does push whatever you’re wearing against your back and keep it there so still not as good as nothing on your back, but better than a laden bag pressed against your back.