I bought this system for my K1300s (used, but the review should be relevant).
First, let's point out the obvious...it's pricey. However, I still feel that this is worth every penny. From using your bike key to lock/unlock/remove the bags, to the expandability, to the ease of removal...this thing is slick.
Quality is also excellent (exactly what you'd expect from BMW). I don't see how this thing would ever wear out it is pretty robust.
Installation takes 10-15 minutes. Plus, when the bags are not on the bike, you won't even notice the mounting system (which is not the case with some others).
There are two waterproof bags that come in addition. For a light rain, probably not even needed.
One of my more expensive and best upgrades.Rating: [5 of 5 Stars!]