I've had a Super-ego for 5+ years of heavy use. I've been impressed by how pristine it still looks. Yesterday I discovered a safety feature.

I was on my bike for a short transit around a mall, and unknown to me did not have the lap belt fastened. Suddenly I felt a jerk on my rear wheel - like something getting stuck in the spokes. Uh-oh. The bike kept rolling, and I pulled over. One of the lap belts had gotten caught in the spokes. But there was no damage:
  • No damage to the spokes
  • No damage to the belt, or to the spot where the belt is attached to the bag
  • No damage to me.

How? Turns out the belts are not sewn on - they are fastened with a very sturdy "tongue" design, but one that gives way before anything rips. So the belt had pulled out cleanly and was on the street. Took me a minute to figure out how to re-fasten it, then off I went.
What impresses me almost as much as the safety release is the strength of the fastener in normal use. An ideal combination. Maybe it's a side effect of interchangeable belts - but it's still impressive. Someone put a lot of work into getting the design exactly right.