There have been quite a few screenshots posted showing the new and improved TextEdit.
The interface is mostly unchanged from the Tiger version, however.
Not like there are too many things that you "can" change in a basic text editor.
Sure, there is the ability to open and save as OpenDocument Format and Microsoft's Office OpenXML Format, but for the most part, it remains unchanged from what I have heard.
Hopefully this is just because the subtle nuances of it's changes have not yet been made public.