When people say "the devil is in the details," what do you think they mean by it?

I’m not looking for the history of this expression or a definition from some dictionary of idioms. I’m asking what you understand by it when someone says it.

It’s been my impression that people use it in so many different ways that it almost has no meaning. So when you hear or see it, does it convey anything to you beyond a general indication that the details are important?