I've heard this argument (I like a single exit point) before, but I don't really understand it, I'd love for someone to explain why they prefer it, if they do.

I think the main reason returning early works so well is that often times, when you're returning different values, it's because you quickly have an answer (often times that something is invalid) for particular inputs. Generally though, there is "real work" to be done after validating or normalizing your inputs.

If that's not true, you're probably trying to do too many things at once, and the different pieces should be broken into separate functions.