I don't use a screen protector yet, but I have a Seidio Innocase coming on Tuesday that has one built in, I'll let ya'll know how I like it
I have the Seidio Rugged which has the built in protector. I couldn't push my bottom buttons.
I don't think it's foolish to have a protector, I just think that it's hard to scratch glass. You can't do it with keys and anybody that says you can has keys made out of diamonds. I suppose it's possible to scratch it with sand but I've never experienced that.
If it gives you the fuzzy warms then get one.