How hot is the perfect cup of coffee?

There is no accounting for taste. (original answer)

This is a bit subjective, after all temperature is a matter of personal preference. Some coffee is served iced as well!

For brewing the industry considers the best temperature to be between 92 and 96 degrees C (197.6 - 204.8F) for 90% of the contact time with the grounds. There are techniques for faster brewing that use higher temperatures according to the final product that you are attempting to make. This induces a slightly burnt taste that some people like. Lower temps bring out more bitter, light tasting coffee.

Back to my coffee... cheers!