A few thousand words on the Mountain Lion document model, the auto save model, how it differs from previous versions of OS X, and so on. Does this really need to be so complicated? I very much prefer the way Sublime Text handles this problem: a document is continuously auto-saved to some secret location, with the changes only written to disk when you explicitly hit save. As soon as you make some changes to a document, the “unsaved” indicator in the tab changed to “unsaved”, but if you quit the editor at this point: (a) there’s no prompt to get you to save “unsaved” changes; and (b) if you restart the editor, you get everything back the way it was before you quit, including the “unsaved” indicator. (It doesn’t save the undo stack, I just noticed, so it’s not perfect, but it’s so much better than the confusing muddle of Mountain Lion.)