I've had them 8 months now and no problems. If something was to get lodged into the seal on the inside that could scratch the film, I'd imagine it would be relatively big and you'd pick up on it fairly easily. Remember, the film can only be scratched by stuff on the inside seal of the door window, and this part is easy to keep an eye on.
As long as you go somewhere reputable and established with a good track record you won't have any problems.
Once the film was applied the guys told me not to use the windows for at least 3 days to let them dry and set thoroughly, during this time there appeared to be a few marks and bubbles which I got a bit worried about, so I phoned them....they said to be patient, and wait...and sure enough, after the 3 days all the marks were gone.
Like I said, you pay for what you get, get it done on the cheap and you may regret it, I've had absolutely no probs!