My favorite Hammerspoon use is binding applications to hotkeys, e.g. Ctrl-3 for editor, Ctrl-4 for terminal, Ctrl-5 for browser, etc. It is so much faster going directly to an app than cycling through the apps in the alt-tab switcher.

Additionally, I use it to bind caps lock to escape, unless it’s pressed with another key, in which case it’s curl. So it’s great to not need Karabiner anymore.