Anybody running metal flat fenders painted? Do rocks slinging off the tires dent the metal and chip the paint?

Most people opt to have them PC'ed to avoid the possibility. If they are painted correctly, it will minimize the likelihood of chipping (except for the underside).

I painted mine but thats because I want to be able to easily touch them up after a few trail runs. If you do paint them you will chip the paint and need to touch them up, but I have had better luck with spray on bedliner.

I run the bushwacker fender flares, and haven't any problems with them, so I wouldn't think you would have problems.