They're not as tough as IS/BSE but they're definitely not flimsy. I've used 3 out of my 15 pack so far and I bought the pack back when they first offered the updated 8700c style. I messed up the install of the first one. The second one started to peel at the edges after several weeks. The third time was a charm, apparently. There are maybe 6 tiny, tiny bubbles that have never gone away but you'd have to be really picky to even notice them.

Granted, IS does have the lifetime replacement and full-body coverage. The latter might have helped when I dropped my 8700c on concrete but it's really academic IMO until someone with an 8700 and IS actually drops one onto a hard, rough surface.