Wow. This hint actually got published on MacOSXHints. I have a few more in the pipe. Maybe they will be too. Either way, you can always find them here. This is my latest discovery:
In TextEdit you can now use undo and redo after (that's right, after) you've saved your document. That is, create a document, type some text, save it, make some changes, save it again, and then hit undo. Voila! It works. In previous versions of TextEdit, after you saved the document, the undo/redo history was gone. Now it's not. Hell, if you want to, you can undo all the way back to the beginning when there was no text in your document at all. Even after you've saved ten times. Neat-O! Just remember, though, once you've closed the file or quit TextEdit, the undo/redo history will be gone.
Now I admit, this is a small hint. Not earth-shattering in the least. But it's been a great thing for me. I write a lot of shell scripts in TextEdit, and you have to save changes to the script to test them out. This means I can now make changes to a script-in-progress, test it, and if I don't like the changes I just made, I can revert it back to its previous form. I like that. A lot.