Use contentEditable in FF.
There are a number of known bugs when the only content in your field is
inline (e.g. just text, no block elements):
-indent is a noop and then DOMSubtreeModified events stop firing until
the structure of the DOM is changed (e.g. make something bold).
-inserting lists inserts just a NBSP, no list!
Once those two are fixed, we should have one client guinea pig it and put
it through a QA run. If we can file the bugs with Mozilla, there's a chance
they'll fix them for a dot release of Firefox 3.