I started using Emacs because I was interested in learning Lisp (and had been using vim for several years, so I figured it would shake things up). The thing I've seen that best captures how full-on Emacs wizardry looks is Marco Baringer's Slime screencast (http://common-lisp.net/project/movies/movies/slime.mov). It's a sort of IDE for Common Lisp. (Edit: Better link, thanks kirubakaran.)
While really learning the nooks and crannies of Emacs's functionality can suck up a lot of time, it's also not going anywhere. I've only been using Emacs for about three years now, FWIW, but I'm a bit of a toolsmith, and I've learned enough to teach others. (FWIW, I'd also jump ship if a better editor comes around, but Emacs and Vim are each good enough that getting sufficient momentum with a new editor to displace them would be incredibly difficult. The most interesting alternative I've seen is Acme / Wily from Plan9, but I don't like its mouse-y interface.)
The best way to learn Emacs is to start with the tutorial (start Emacs, then press Control-h and then t), and then learn how to use the built-in help system. Everything is meticulously documented, though sometimes with unfamiliar terminology. It helps if you have a focus, like learning how to run make, a Python interpreter, etc. inside it. The Emacs Wiki (http://emacswiki.org) has quite a bit of good advice, as well.
Don't forget to keep your Emacs config under VC. :) Extension recommendations - pabbrev, tagging.el, uniquify, saveplace, recentf, remember, midnight, anything, and emacs-w3m if you're using Unix.