Mountain Equipment Co-op... bought these 6-7 years ago and they get used on a pretty near daily basis for everything from commuting, to touring, to utilitarian tasks and they have been great. They have a single main compartment (simple), rear pocket, and another pocket in the top flap which is accessible when the bag is open.

Sadly, they no longer make this model so if I ever wanted to use the lifetime warranty I would not be able to replace them with the same panniers.

Shown here on the back of my Cascade (tourer) with the newer touring panniers up front which are also really well made (ballistic nylon construction).