Ranked in these QuestionsQuestion Ranking
Pro Deeply customizable
Hammerspoon's Lua scripting and broad API allows you to perform any action you can imagine on your mac. It hooks into many OS APIs directly and has some high-level APIs to manipulate things like Spotify or iTunes. See the full list here.
Pro Automate actions based on the operating system
Hammerspoon lets you hook into OS level events and trigger any action you can imagine. From setting up a simple keyboard shortcut to launching a complex workflow using multiple apps and scripts.
Con Some knowledge of programming required
Hammerspoon is scripted in the Lua programming language, and some familiarity with programming in general will be needed to use it. Some plugins exist that can be used by adding some files to a specific folder, but this will not give the flexibility that is so key to Hammerspoon