I know these are cheap, but they aren't as cheap as the un-branded ones available on here and in other online marketplaces, but they most certainly should be.
Within 2 days of having this protector on my new blackberry, the protector had gained a ridiculous amount of scratches, so much so that i had to apply the second protector that is supplied. These scratches didn't even come from ridiculous usage, it was pulling the phone out of my pocket, and placing it back in said pocket. I believe the ability to withstand this usage is a pretty basic requirement of any screen protector.
on a more positive note, these protectors are easy to apply (a good job too coz you'll be doing it lots if you buy them) Hope this was helpful