I was once told in no uncertain terms to stop using the letter in my talks. I disagree. I think it’s a great letter, especially in scrabble.
I just stumbled acrossed this great page by John Kerl, which contains numerous tips for handwriting in mathematics. I think I differ in one or two places, but I couldn’t agree more with taking a moment to think about it. Maths is communication for the most part, starting with one’s own handwritten notes.
On the subject of excellent references about mathematical communication, I also really enjoyed reading The Grammar According to West, which is something of a Strunk and White for maths papers.