While I can't speak for the 1520, but I've never used a case or a screen protector on any of my phones. Never managed to break any and I bet that many of my phones still look more pristine than those worn in cases by some people
What's the point of buying a beautifully designed phone with a gorgeous screen with oleophobic coating (the high end Lumia screens just feel amazing!) and whatnot if you cover it all up with ugly casings!
I just purchased three Headcase Designs covers for my phone. They're similar to the Incipio and other rear shells, but are only $8.50 each and have nice design options. I'm pretty happy with them.