So, like an increasing number of folks I know, I'm a Switcher. I forsook the Wintel way for a 12" PowerBook, and have been quite happy.
Among the things that happy-makes me about OS X are the nifty shareware tools acolytes built for it. That was something I remember from being a Mac owner "back in the day" -- a lot of the coolest stuff were wee add-ons created by crazed fanatics.
Among the most popular pieces of OS X shareware is the LaunchBar. It's a utility that makes finding and launching applications and files in your system much easier -- just type a few letters, and it 'knows' what you want, hit "enter", and it's launched. It's surprisingly useful, and also somewhat shocking this hasn't been thought of before.
Because I'm a total interface design dweeb, when using it, my first thought as, "This must be what the Canon Cat was like." The Canon Cat was a computer designed by Jef Raskin around 1987, which was totally controlled through keyboards. Not like a normal command line interface, though.
The Cat's user interface made this computer unique when compared to other computers. The user interface was based on a simple text editor in which all data was seen as a long stream of text broken into pages. Special keyboard keys allowed the user to invoke various functions. An extra key titled "Use Front" acted as a control key. You pressed Use Front and then a special key to activate a specific feature. For example, the L key was marked Disk, the J key was marked Print, and the N key was marked Explain (Cat's context sensitive help facility). Other commands existed which let you change the system's various parameters (Setup key) and reverse your last action (Undo key). ("Canon's Cat Computer: The Real Macintosh")
It turns out the Mr. Raskin is also working on developing an interface. "The Humane Environment" or THE, to be exact. It's sounds a tad mystifying.