Exclamation Point!

There are people who overdo the exclamation point. "We went to the beach!" "The coffee was extraordinary!" "Cranston lost his keys!"

Others would endure torture instead of adding what they regard as an unnecessary and gushy form of punctuation. 

I take the middle ground and occasionally use exclamation points for a simple reason. Writing is akin to performing on a stage. Stage actors, as opposed to their colleagues in films, have to exaggerate a bit more in order to project an emotion. They don't have a camera examining their every pore. It is far easier for a film actor to be subtle than it is for the stage performer who must be heard by the people in the balcony and the back row. That is why the "stage whisper" was invented.

Writing poses a similar barrier. Consider this scenario:

An associate sends an idea via email.

You email back: "Great."

Your friend may stare at that and wonder, "Is that 'great' what I mean by great or is it a reluctant great, a cursory great, an 'I can't believe you think this is a good idea" sort of great?"

An exclamation point - "Great!" - conveys sufficient enthusiasm to overcome the potential misinterpretation.

This is, of course, neither fool or knave-proof. Some may use exclamation points as a form of sarcasm. When they do so they risk misdirecting their barb. If you are going to be sarcastic, you want people to know it. 

Others may read too much into the exclamation. They may not know your currency exchange rate. "Great!" may really mean "That's very good" or even "That's good."

Set those quibbles aside. If the exclamation point is appropriate, go for it.

Remember, when they cannot see you or hear your intonations, you are on stage.