> My only complaint is that I can never get Emacs's indentation to match what Prettier wants to do, so I'll type a bunch of code, prettier-on-save, and everything gets moved around.

I had this same issue, and it was annoying enough I continued to use https://github.com/editorconfig/editorconfig-emacs alongside prettier.

This does create another annoyance in having to configure editorconfig for new projects instead of relying on prettier alone.