I love them and use them everywhere I can, mostly with JS/TS. I find the code displayed with ligatures more readable, and the only time I notice any overhead is when modifying === to !== or back, when I have to remember that I have to change only the initial character. Having => as arrows instead of `equals+more than` is enough of improvement, for me, that I keep using them, even without all other tiny tweaks that they give you.

I used to use "Fira Code", but then I've migrated to "JetBrains Mono" everywhere.