I've never had an Ortleib bag, mainly because I'm cheap. I've got Axiom panniers that I love and I keep an Ibera rain cover in each one for emergencies. Since I don't do 3 day treks through constant rain, this cheaper set up is working for me.

But I fully understand the value in a higher prices Ortleib bag if you're in a rainy climate and constantly riding in the wet for any reason. They seem like very well made bags.