MI isn't a bad choice for formal, but seems to have a more playful and almost Jolly Rancher vibe to it sometimes so I don't reach for it in those situations. Formal situations are normally my excuse to wear my unquestionably masculine scents.
So long as its in the summer, I can wear this to any occasion. If the night is very hot, I could still see myself wearing it (wore mine this year to a wedding in a baking hot climate in early June on an event with a suit and tie).
If the temperature cools down a bit another formal evening option would be Aventus for me.