I know someone who's had it done, but since having it done it's never been broken into so it's hard to tell if it stands up to the claims.
As most cases of vandalism will be time sensitive, the chances are they may just give up and move on if they don't succeed as the noise of trying to break through will be too great, and it will just be too hard.
My ONLy fear of this stuff is whether it would lead to retribution / repercussions from the thwarted thief, but then you cant live live worrying about such things. I was going to get fronts done with it, but now the wife has decided she wants 19" rotors on the car rather than OEM 18's so my budget for tinting has been shot out the water for at least a year.