I am totally off of using screen protectors. I used a protector for the entire period of time I had my OG Focus. I started with whatever the at&t store had on stock, and I wore it for several months. I eventually got a Zagg Invisible Shield for it. That was used on my screen for at least six months, until about a month before I was ready to upgrade the phone (I was waiting for the 920 to launch). It was unbelievable to peel the protector off the screen. Even with keeping it clean, so much grime and gunk accumulated on the screen protector that the bright, vivid OLED screen had appeared washed out and blurry. The change was so gradual over time that I hadn't noticed until that screen protector was peeled off. I carried the Focus for at least a month screen protector free, and didn't get any serious scratches or anything.
So, when I bought my 920, I carried it as is. No case, no screen protector. It is well worth it. I may have one or two little scratches on the screen, but to me, that is far superior to a grimy screen protector making the beautiful display on new phones look crummy.