Pros: The BEST product I have EVER spent money on. More precious than my bike.
Cons: These bags become what you worry about getting stolen. Not the contents or the bike!
Before I started a bicycle trip from Ohio to Alaska, I went to many bikeshops and asked for the best pannier money could buy. I was eventually sold a very expensive set of Cordura (artificial canvas) panniers made in a Californian town that practically never sees rain. On the Alaska highway I started meeting European bike trekkers and they all had Ortlieb panniers. I couldn't believe that these were completely unknown in the US at that time (1997). The first set of Ortlieb panniers I saw had been around several continents and looked really worn, but functioned perfectly with no real damage. My first reaction to these bags was that they looked lightly constructed. I thought the plastic hooks were weak. Seeing other people's bags that lasted for 50,000km + was one thing, but now I have my own set that has seen many transcontinental crossings as well as daily service as commuting bags. I actually ordered a spare hook assembly to carry in reserve (with 2 people and front/back Ortlieb bags, that's 16 that could go bad), but have never had to use it. It's nice to know that replacements are available if you do manage to break them. I have wrecked with these bags. I have ridden too close to concrete and brick walls. I have ridden them into posts. Scratches, but no real damage. The main issue with Ortlieb isn't actually it's outstanding longevity and durability, it's the Wasserdicht (waterPROOF) feature. This bag completely changed my wet riding mentality. The bags made in S.Cal (of the common pannier design) are completely useless in the rain (or even on wet roads! remember, in a desert, it might not rain a lot, but if it does, drainage is bad and standing water can be a real nuisance). With normal bags, you'll double your gear management effort with ziplock bags. With Ortlieb (any product), you just dump your stuff in and forget about it. I've had my loaded bike strapped to the railing of a small ferry in high seas where it was getting pounded with waves. I was worried about the salt water on my bike, but I knew that my camera was safe in my Ortlieb. Also, don't forget that waterproof means bug proof, dust proof, sand proof, smoke proof, skunk proof, mud proof, etc. Trekking in the desert is dusty business and Ortlieb is a great asset. I have had my Ortlieb in huge temperature extremes. From the blazing heat of Death Valley, to 3000 meter Colorado passes in winter, I've never had any temperature related issues with the materials. My panniers are all black and green (the most stylish if least safety oriented choice) and I am amazed at how cool the insides stay even when sitting in direct blazing sunlight. Another issue that comes up with Ortlieb is its lack of pockets. Too many people (I learned the hard way) choose panniers based on gimmicks and how many pockets. It turns out that in real life, these pockets drive you crazy. If somehow all your gear would magically fit each pocket perfectly, that would be helpful, but it hardly does. Even in this idea case, you still have to deal with the fact that if the slightest bit of rain appears, you have to totally reorganize your strategy. Either every thing must be put into plastic bags or moved into the main compartments (which are full with other stuff) in a bigger waterproof system. Maybe you envision putting a shampoo bottle or things like that in the multifarious pockets of normal panniers. That's fine, but I found that 90% of my stuff was stuff that would be very unpleasant if it got wet. Non Ortlieb people have told me that they like how fast they can get to something with all the pockets. First of all, I had a hard time remembering what was in each pocket. It's bad enough trying to remember front/back,left/right. But I found that I can remove my pannier from my bike, empty out its ENTIRE contents pick out what I want put everything back, seal the bag, and mount it on the bike again all quicker than most people (certainly me) can locate and extract a ziplocked item from a specialty pocket. This brings me to my final Ortlieb miracle, the mounting. With my California bags, the mounting system was made so that if the bike with panniers was put into a scrapmetal grinder, the pannier mounting hardware would still be attached to pieces of the rack. That's nice, but making a rack attaching system that is stronger than the rack just doesn't make sense. I remember dreading taking off those panniers because it was such an ordeal. Ortlieb on the other hand has an ingenious system where the bag is held to the rack with a clip that has a retractable retainer. This keeps the bag from jumping off when you hit a bump. To retract this retainer and remove the bag, you simply lift the carrying strap. Magic. That is why I can remove, empty, repack, and replace my panniers quicker than people with normal panniers can mess around with a curved zipper. This brings me to the final point about Ortlieb which is the fasteners. Zippers on traditional panniers are just liabilities. They freeze easily. They get jammed with mud and the aforementioned ziplock bags. Eventually this is where most panniers fail. Ortlieb uses fastex clips that improve any situation where they can be employed. Ortlieb actually changed their clip style from the frist panniers I bought to the ones they sell now. I like the old ones better, but I've never had a problem. The whole rolldown closure system provides great flexibility. If you buy a bunch of food and need the extra space, you can ride with the panniers completely open and just filled with temporary stuff. In summary, I love my Ortlieb bags. I now spare no expense with bags (though they are not more expensive than the most expensive bags non waterproof bags) and buy Ortlieb for every application I can. I love the mounting, the simple compartment design, the lack of zippers, the durability, and the absolute waterproofness. This is simply a great product that I wish was more well known in the US.