I find it doesn't really matter what I'm interested in (computer-wise)---Emacs has me covered. It saves a huge amount of time to not have to relearn a new IDE each time I need to switch programming language. There is always more about Emacs to explore, but it is well invested time, as I know that Emacs is going to be around most likely for the rest of my life-time. The killer features for me are:
+ Org-mode
+ SLIME (Common Lisp IDE)
+ A Lisp as "extension" language (it isn't really extension---Emacs is fundamentally reprogrammable).
+ Really smooth integration of LaTeX, Dot and Tikz.
+ Rock, rock, rock solid no matter what I through at it.
Also, I find that for me, Emacs has ergonomically good key-bindings once I accepted that they are different, learned them properly and did the CAPS-Ctrl switch.
+ Org-mode + SLIME (Common Lisp IDE) + A Lisp as "extension" language (it isn't really extension---Emacs is fundamentally reprogrammable). + Really smooth integration of LaTeX, Dot and Tikz. + Rock, rock, rock solid no matter what I through at it.
Also, I find that for me, Emacs has ergonomically good key-bindings once I accepted that they are different, learned them properly and did the CAPS-Ctrl switch.