I've used the Nashbar waterproof rear panniers for a few years now on a number of short tours and also general utility trips (grocery store and other shopping). They're holding up well and still look new. I did encounter a problem when using them on one of my bikes with a rack that doesn't have a support arm very far back - a couple times one of the panniers swung inward and hit the spokes of the rear wheel. Since then I only use them with a rack where the rearmost support strut extends farther back.

They're very basic - just one large compartment and non-locking hooks. But they seem to hold up ok and have quite a bit of carrying capacity.