Magit, ESS, SLIME, Cider, Gnus/mu4e, dired... There are some fundamentals that make it relatively easy to pick up anything: * Help system (nearly everythi

Magit, ESS, SLIME, Cider, Gnus/mu4e, dired... There are some fundamentals that make it relatively easy to pick up anything: * Help system (nearly everything is self-documenting) * Customization * ELisp basics (write some helper functions in your .emacs) * Debugging (Edebug, just do C-u C-M-x to instrument a fn and step through it next time it's called) I've been a long-time Emacs user, and the "aha" moment happened when I realized that Emacs really boils down to three things: 1) a text editor 2) mechanisms to interact with your system (e.g. subprocesses) and 3) interactive and dynamically programmable runtime. Once you learn the fundamentals of those three things, the sky's the limit...