There's one independent in town that I'll go to; a garage that's been operating since at least the fifties (longer, even, I think). The sketchy Citgo/BP/Mobil? Not a chance, for all the reasons mentioned.
Even the newest, 'cleanest' ones have two-day-old cold coffee, "Not for Resale" 16oz sodas and snacks bought from the grocery store and marked up 200% or more, and bathrooms that are for paying customers only yet have apparently never been cleaned. Oh, and if you do want to be a paying customer by credit card, there's a five dollar minimum.
They're getting decimated by Kwik Trip in my neck of the woods, although they're constantly trying to get local governments to prevent the competition.