An extensive article explaining the Cocoa text system (especially how to modify the key-bindings, brought to my attention by its author Jacobus Rus at Macworld while visiting the TextMate booth):

• Cocoa Text System
  Apple’s Cocoa text system is a complicated beast, but also extremely flexible, and with a bit of work, it can be molded to match many working styles. This how-to covers the 2 major ways of customizing the text input system: Default key bindings, and for
  (tags: macosx cocoa input text)