For one, the retention system was somewhat ghetto. It was mostly a bungee cord, with a hook to put around the bottom of the rack. It was not very secure, and one big bump, and the pannier is rolling down the road next to you.
Also, the zippers seamed to always get caught for me, at one point it was caught so much I had to yank hard, and I felt as if it almost broke. Not something I want out on the road.....
They probably are not too bad, but I am just so happy with my Cannondales, I see no reason to use anything else.
Tim