I have never used 1 of those on my droid bionic can I have had it since the first week of release. I don't think many people actually know the history of gorilla glass, it has been around for 50+ years. It is as strong as hell, about 2 or 3 * stronger than regular treated glass. I work in a shipboard environment, along with an office environment, and I drop it all the time and it has not scratched it yet... Those films that they sell are only to make money and came out before gorilla glass became more popular and served a function before, but now it is not needed IMO. That will be your choice though, but I have put my phone through a lot of stuff and is still going great without that film...
IMO, spend your money on a quality case to protect the edges of the glass, because that is where it would break if it did break... Unless you slam it with a hammer, in that case the film wouldn't help you anyways .. LOL