I cannot begin to tell you how awesome all Ortlieb products are (I also have the Trunk Bag). I do not have any experience with other panniers because I read all the reviews of all of them that I could, and determined these to be the best fit for me (they may not be for you, which is OK). First of all the QL2 mounting parts are great, and I have bumped and thumped the whole bike many times and it all stays attached and does not rattle or dismantle. Others might mention that they do, but I decided to read the manual and follow instructions rather than pick up parts off the trail and my efforts have been rewarded. The handle latches that really hold them onto a rack are great. The only issue I have ever had (which confused me for a bit because it was hard to see) was that a tiny rock had somehow gotten into the TOP of one of the latches, just look out for it, but it is not really a problem. I also wanted the compression straps, and they are great. I made my own security cable kit thing, but I recommend you get that at the same time as you get these, you will want it once you see how easy they are to take off and replace securely (Ortlieb Pannier Security Cables-Short).
I am touring the Northern Tier this summer and got these panniers in hopes that they would be durable and waterproof and Ortlieb is yet to let me down! This pannier can carry alot and is extremely durable! The outside feels and looks like a rather denim type material but it is 100% waterproof.
The mounting system on these is genious and can really fit any rack. There is a rotatingsliding hook that grabs your rack to prevent it from shaking or sliding. This hook can be removed and put on the second track to cover a range of mounting positions and then tightened to lock in place! This can all be done by hand with no tools!
I used these panniers on a three-month cross-country tour, and I've used them for a couple shorter tours since, plus the occasional grocery run, etc. They're great! The lid system is (IMHO) easier to deal with than the usual roll-top, and unless you're dropping your bike into a lake, will keep your stuff just as dry. The fabric is 100% waterproof. I found the outside pockets convenient for smaller items that I wanted to access quickly without digging around in the pannier's main compartment - I kept my flat repair tools in one of them. I did get a small abrasion hole on the outside of one of the pockets when I rode my bike down a very narrow sidewalk on a bridge with a concrete barrier that the pannier rubbed against. Totally my fault, and I repaired it easily with gear repair tape that I'd bought to fix a hole in my tent. I treated these panniers very roughly - tossed them around, leaned my bike against anything and everything, and so on - and they're in great shape except for that hole.
I love Ortlieb's attachment system; once you get everything dialed in, getting the panniers on and off is easy-peasy, and they never move on the rack. I did lose one of the lower attachment thingies on one of my front panniers - so, not this pannier exactly, but they have the same attachment system. Now I check to make sure everything's tight and secure every once in a while. No biggie.
Much nicer and more convenient to get in and out of than my Back Roller Classics that I sold immediately after getting my Bike Packers Plus . I waited to see them on sale and got such a good deal I bought the matching Sport Packers for the front as well .
I've been using these for touring about a year now, and just last month put them through their most strenuous test snow camping at the Crater Lake rim. They are most definitely 100% waterproof, and although at first I wasn't sold, I've come to love the closure system on these more than on the classics. And the outside pocket is amazingly convenient, its flap-top closure is brilliant and secure. These are truly the best of the best when it comes to panniers for extended touring.