In my earlier days as a gamer, even up until just a few years ago, I thought these things were garbage. Useless, even.
Then, the boy came along. He certainly doesn't mind eating 16 slices of pepperoni, and then manhandling his DS phat.
So, I at first would vigorously clean them when I noticed a smudging. Then I remembered: "those useless screen protectors!!!"
Put them on. Ugh, now I remember why they were shit- They bubble and blur the initial screen. But, for him, it was good enough.
In short- if you're an adult who has trouble keeping things clean, odds are you need more than these screen protectors. But for parents of uber-young gamers, these are legit.