Similarly, the rhyming tools are interesting, but make them hideable for anyone who is not using them. I would use a thesaurus a thousand times more often than a rhyming dictionary.
I actually like the fixed-width font but suspect many wouldn't. Maybe an option to switch between fixed-width and not. Also, I expect to be able to use the tab key to indent, but it doesn't work here.
Saving and revision control would be great.