I am a little surprised there are as many votes for bed liner as there are. I tend to think those in favor of the bed liner don't use the sliders to their potential, or at all. More expensive and a lot harder to touch up... although I am not familiar with the rustoleum spray stuff floridaoccifer
mentioned. Those seem to be only $11-$13 a can and maybe don't require as much BS to apply.
I personally would stay away from hard paints like rustoleum enamel and hammered. They chip easier. If you don't have much rocks/gravel in your area maybe that's not a concern. I live in the rocky desert, use the hell out of them, I'm cheap, and I want easy touch-up. Rustoleum Satin, $3.50 a can works great. If I had a nice shiny vehicle and cared more about looks, and didn't wheel as hard, I might consider a liner... bottom line it's contextual.