omg, opt-esc, global hotkey for cocoa text fields to try to complete the current word, try it!
there's also tons of other stuff like ctrl-k and ctrl-y (like cut/paste, but with a separate buffer, and cuts to end of line instead of using a selection). or ctrl-a and ctrl-e (move cursor to start/end of paragraph). and you can also make your own hotkeys including ones to do multiple things, like i made one to duplicate the current line by piecing together several commands. they also allow hotkey sequences as triggers.
i also just found out about the esc based shortcuts in terminal (press esc, let go, then hit key). esc-d, esc-delete, esc-f, esc-b :-D (those are forward-delete-word, backward-delete-word, forward word, and backward word)
apple does a great job with details like this, when they try. i hope OS X gets more love soon (though i accept that iphone os is more important to their business atm)
# in terminal