Could we rethink the notion of 'help'? Currently 'help' is basically man pages in windows.
the Wetpaint wiki hosting service has a feature on their site called Orientation which tracks which features of the wiki you have used successfully so far and (presumingly) gives you tips for those features you have not used yet. A generic framework for something like this would be great in GNOME - basically the system assist your training. (I realize this idea taken to the extreme is Microsoft's Clippy - the lesson from Clippy is: don't take this idea to the extreme)