The idea of waterproof panniers is great, but none of the panniers I have purchased over the years have been. Water resistant, yes, but not waterproof.

But I tend to avoid the rain, preferring to hang out in coffee shops and greasy spoons, or seek shelter under a porch.

I have ridden in the rain, sometimes for hours, but for some reason, my water resistant panniers have kept my stuff mostly dry. Maybe not perfectly dry, but my things have never gotten completely soaked.

I would probably switch to waterproof if I were carrying a down jacket, or an expensive camera, or some item that would be seriously damaged by water.