Master Emacs in one year
github.com
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For example, when I'm writing Java, I use Intellij -- but sometimes copy an argument list into Emacs to do quicker macro-driven editing.
For basic text editing (emails with no formatting, simple config edits, etc), I think the difference between Emacs and vim is a matter of taste.
But once you want to do complex things, Emacs becomes possibly the only option. It can be made into the best Git tool I've seen (Magit), a great outlining/scheduling/TODO tool (Org mode), multiple great Lisp interfaces (CIDER for Clojure, SLIME for Common Lisp), and even just running a shell inside Emacs makes for really nice integration for writing shell scripts.
I certainly won't argue that it's the perfect tool for everything, but it's a great malleable general-purpose tool.