I try to avoid them, it's really, really last resort stuff. And I hate the litter, the people that use these places regularly think nothing of dropping the brown paper bag out of the window wherever they happen to be sat, whether it's in some rural beauty spot layby or 3 feet from a bin in the car park. It makes me feel really sad.
I'd be genuinely happy if they died a death and the regulars were forced to give their custom to something else, but it won't happen.
If I'm middle of nowhere, and cold and hungry, I'll use one, maybe once a year or less. Otherwise, no thanks, I'm sure I can find somewhere I'd rather give my money to.