Auto Save in Lion, users objected, was thus a potential trap, an invitation to cause the very thing it was supposedly designed to prevent — accidental data loss. The data might not really be lost, since the Versions database might hold an acceptable earlier state of the document; but finding that state in the clumsy Time Machine-like interface wasn’t easy. And what if, after saving a problematic change that you weren’t even aware of, you closed the document and didn’t return to it for days, perhaps weeks, opening it later only to be horrified and confused? Would Versions help you understand what had happened? Would the database still contain the desired document state? It all seemed so backwards, somehow: first make a drastic accidental mistake, then later discover it (if you’re lucky) and scurry around trying to fix it — whereas, prior to Lion, you would have been alerted before making the mistake of saving the faulty document in the first place.
Please note, though, that I’m not claiming to be entirely happy with the Modern Document Model. Actually, to be quite honest, in my view, Auto Save is itself a massive mistake, an utterly erroneous pretense that the desktop is like iOS. Its deeply flawed nature is well revealed by what happens when you edit a file on a mounted remote disk: you get Auto Save without Versions, which even Apple has admitted is troublesome; see Adam Engst’s article on this topic, “Beware Lion’s Versions Bug on Network and Non-HFS+ Volumes,” 8 September 2011.
He also explains exactly what the “Close windows when quitting an application” checkbox does, which is not quite what I first thought. It does makes sense when you think about the new document model, but perhaps it would be better off as two separate options.