I use Hasklig, even though on a different language. I love having ligatures for common symbols. I should pick up fontforge again and adapt it to PHP
The use of ligatures in Hasklig is very intriguing. Would really like to see more work in this vein. Could see benefits to Clojure (arrows) and even => in JavaScript.
EDIT: Looks like FiraCode has ligatures too https://github.com/tonsky/FiraCode