Specifically for programming I cannot see why you would use this as opposed to something like Visual Studio with its context aware auto-complete (massive productivity increase).
But then again I also don't get why someone would use Vim or Emacs when you have GUI based tools available (even freely). Even for non-Windows programming Eclipse exists and has a decent (if slow) context aware auto-complete for many languages.
The only justification I've ever heard for people's continued use of tools like this boil down to either "I know the shortcut keys" or "I don't have to use the mouse."
Which to me is odd within its self as very little of my programming efficiency is lost mousing around, and a lot more lost having to jump around code blocks because auto-complete didn't magically know what an object's members were...