I've had the small white for a couple of months now. I've got a tube, levers and patch kit inside, with a multi-tool in its separate pocket. It fastens securely, and I never feel it moving, or rubbing my legs. I guess my complaints come from having the white version. It experienced its first rainfall the other day, and the next time I rode, I noticed that it had developed brown-ish spots on the white material where there are tools inside. I know it's picky, but it just looks dirty. Also, the white zipper seems to be fading to a yellow-ish tint from the sun.
I like the bag, but if I had to do it again, I'd go with black.