Well, without Emacs, I wonder what I would have coded and how much!
Once you know how to configure and use it correctly and find the modes for your needs, it's the ultimate toolbox for any text editing you need to do, from coding to document writing.
Emacs is more than an editor. It does everything I need: from chatting to email, and even some text editing!. It doesn't have the leanest learning curve, but every single minute spent on learning emacs becomes hours of saving time latter. Totally worth it!
A recent discussion in the Emacs group on LinkedIn (http://bit.ly/7HAB3P) was headed: "Wouldn't it be cool if emacs expertise was somehow useful in finding a job?" The most penetrating response to this question was "Emacs expertise is actually useful in keeping the job." This is in a nutshell the reason I use Emacs. All the horror stories about the Emacs learning curve are true, but once you've achieved the summit, you are positioned for serious productivity gains--and without knowing a scrap of elisp. Rectangular cut and paste, line sort, and regexp replacement (sans mouse) alone have saved me dozens of hours of data hashing that my biologist colleagues would have spent clicking and dragging in Excel or worse. All my perl development (perl-mode) and debugging (gud) happens in Emacs, as well as all my remote site editing (ftp-ange), wiki pages (wikipedia-mode), and html (html-mode). I rarely open a Word document, except to paste in text composed in Emacs.
Etc., etc., etc. If there is a problem with Emacs, it is that it trains you into itself. When in another IDE, you feel like Steve Mann at airport security (http://bit.ly/6FLtNj). Consequently, this cannot be an unbiased review--for example, Eclipse sits idle on my hard drive, taking up however many hundreds of MB of space, because it's just not worth retraining my fingers. Maybe one day, after this quick tweak to bioperl-mode...
When you make the leap to coding your own packages, you might as well abandon hope of ESC ESC ESC. You'll have finally crossed the separatrix and are trapped (http://bc.tech.coop/blog/060302.html). But it's a happy place. Your hands are always on the keyboard working away. And as Zippy sez:
"...Get me a GIN and TONIC!!...make it HAIR TONIC!!"