EditArea and CodePress are two text editors that are run in the browser. They're not WYSIWYG editors and the most important feature it really actually adds is syntax highlighting. First and foremost I think this is a solution to a problem that shouldn't exist: either you go full-on in emacs/vi/eclipse or you don't do any editing at all.
I seem to remember a EditArea implementation for Zope which replaces the dumb
textarea tags in the ZMI for Python Scripts which was a neat idea but I quite quickly turned it off and went back to the plain vanilla solution. My beef with it was simple: speed. It takes almost more than 2 seconds to load it fully and the browser feels unresponsive for a quite a few seconds even after it's fully loaded. And unlike emacs/vi/eclipse, in a web browser the reason you're editing code is probably because you're jotting down a quick hack or editing a tiny detail. Neither activity means that you keep the editor open for a long time.
Some quick thoughts about the difference between the two: