I think whether a person should or shouldn't use a protector depends on their personal habits & how likely they are to scratch. My Razr replaced my OG Droid, which still looks like brand new aside from the gold colored layer flaked off the camera button. Glass is perfect. I keep the phone in a shirt pocket or soft-lined belt case (along with my wallet, biz card holder, receipts, thin USB drive, and Square CC reader), so it's nicely protected when not in use, I'm generally good about not being clumsy with my phone (dropping, etc), and I'm careful not to work the phone with dirty hands. All these things add up to not needing a screen protector. Some people have to work in dirtier environments, or are more clumsy, etc, and a screen protector may be a good idea.
I do know that a guy I do some work for occasionally has had screen protectors on his smartphones, and whichever ones he's using make the picture look like total crap.