Well, I decided to bite the bullet and give the bag a try, so here are my initial thoughts. Hope they are helpful to others.
First off, the bag looks good (pics attached). Seems sturdy though I haven't really tested that. It's a roll-top design: to close it, you roll it three times and clip the plastic clip together. That creates a handle you can carry it with. It also comes with a detachable shoulder strap - pretty standard, nothing special, comfortable. The strap is easy to take off and stow as needed. There's a smaller zippered pocket in front and a mesh pocket on the back. There are two rigid panels inside that keep the bag's rectangular shape.
It's not a massive amount of storage, but certainly good enough for my needs. I generally carry a 3-ring binder, pad of paper, change of clothes, and big headphones, plus one or two U-locks (depending where I'm going) and that all fits.
It has one big clasp on the bottom that secures the bag to the rack. At first I was dubious that just one clasp would get the job done, but I was pleasantly surprised at how firmly it attaches to the rack. It's very solid - no movement at all. The system to latch and unlatch is very simple and easy. It goes on in 5 seconds and come right off with a good tug on the strap. And yet, as I said, when it's on there that bag is not going anywhere. I'm very impressed with the KlickFix system. I just took a ride on some deliberately bumpy paths and the bag didn't move an inch.
I just got it a couple of days ago, so this is just a first impression thing. But so far, so great. Happy to answer questions if anyone is looking at getting one.
