I used to use protection, but not anymore.
I figure that I will get a new phone in a year anyhow and just don't like the feel or look of a protector. Never had one on my Pre2 and no scratches in one year. However, after having my Trophy for a couple of months, I have one small, light scratch, with no idea where it came from. I can live with it but I don't think the screen is as durable as some phones.
And yes, I do keep it in my left pocket without keys or change, no case.

And yes, I do keep it in my left pocket without keys or change, no case.