So has anyone else out there tried this?
no, but I have experience with the Herculiner roll in bedliner if that is what you are considering. If your rails are metal, then I dont see why it wouldnt work. I have used it on my trucks bed, wheel wells, on a tool box, on a workbench, and even to freshen up an old metal shelf. Just make sure you scuff the metal REALLY GOOD with a green scotchbrite and get it clean so it will adhere to it.
One note about Herculiner, it will fade over time, and they do have a UV inhibitor you can purchase that will help keep it from fading so quickly.
The nice thing about Herculiner is that it is the only bedliner that adheres to itself. I did my F150s bed when it was near new back in 06. It started looking crappy in 2011 so I bought another kit for 50 bucks, washed the bed real good, and applied another coat. Looks like new again!
I will warn you, this stuff is mean. Wear gloves and old clothes. If you get it on you it is a nightmare to get it off. You will literally have to bathe in turpentine to get it off your skin. And once its dried on your rails, its there to stay. FOREVER.
They do have colors other than just black too.