For me screen protectors, the kind that stick to the screen, defeat the niceness of the screen. If I had to have one to protect the screen, I'd rather
not have the device. However, my experience suggest that for me, these screen protectors are not needed. My last cell phone that I used for two years, still has a perfect screen--not a single scratch, and I did nothing special to protect it. And I kept it in my pocket with keys and stuff. I kept my iPad 2 for a year and no problems there.
I even have a blackberry curve smartphone and its screen is in perfect condition. So, I am a person that does not need to worry about protecting the screen. However, I must worry about the back and edges of the device, so I do need a case.