It would be handy to have toolbar buttons for making unordered lists, numbered lists, and indenting and unindenting list items available for the RTF toolbar. I do a lot of outlining, and the support for it in the RTF editor seems weak.
(FYI, I might be putting a whole stream of suggestions in - I’m currently evaluating DevonThink Pro against a bunch of other apps. I really like it so far, and want it to be The Answer).