Regarding prefs, I always thought RTB was missing these:
- Large text areas
- Resizing the prefs window to fit larger texts
- Subtitles or mouse over hints for prefs to tell new users what each prefs does in detail
- Adding seperators between prefs of the same add-on
You could also add a few more cool features that a few add-ons could make good use of:
- Support for adding custom buttons in the prefs section that execute a callback function, for example an add-on could register a button "Clear Stats"
- Dynamically adding/removing prefs or updating values while the gui is open