I just got mine and painted them with the Rustoleum Hammertone for a couple of reasons. First, when we talk about cheap paint vs. expensive, we're talking a one dollar +/- difference in cost per can, and at most, only one can per slider. So after spending $250 on sliders, I might as well spend the extra buck. The Hammertone also patches easily, and the patch blends right in with the rest of the paint, because of the texture.
With flat black, patch spots may be readily noticable, unless you spray over a long area to help hide the actual patch, but it still works. One thing I noticed on another member's sliders, as far as the bedliner stuff goes, they will not just scratch off, but more likely peel off, and must be more of a pain to patch. Right, Tom?