If you mean that piece of plastic that's over the screen, that's not meant as a scratch guard for use. Everything with glass always has a plastic protector that is meant to be taken off after you've gotten your product.
I don't know what you mean by slowdowns on getting 4.2.2, but within 5 minutes of turning my Nexus 4 on, it had downloaded the update and told me, and I installed.
Yes. I did mean the plastic that covers the screen. I have seen many stick to it rather than buy a real scratch guard.
As for the slowdown, you would have noticed if you used 4.2.1 for a few days. You can find more at xda;