Something I've never really paid attention to, and it's actually quite a powerful feature: when doing search/repalce in Emacs you can replace with Elisp code (as in, Elisp code can provide the replacement).
As this article says, I've always tended to drop down to the CLI to delete a branch, and ensure it's cleaned from the remote, etc. Somehow I'd never picked up on the fact that Magit just handles this. And of course, it does, Magit does so much!