I started using Emacs about a year-and-a-half ago because it was the confluence of several wants -- wanted to work with regular expressions (in an editor that supported them), wanted to learn lisp, wanted a better editor.
Editing my code with regexes taught me a lot about finding patterns in the code. The keystrokes took a while to get used to, but I fly a lot faster without the mouse.
Emacs gave me the ability to keep work with my notes and coding in the same application -- minimal context switching means minimal brain-switching, and I can keep focused on the task at hand.
