• It is indeed a new-ish paradigm. So re-purposing old File menu commands with existing mental models doesn’t make sense.
• Also bear in mind that the APIs for versioning are not forced upon an application. It’s up to the developer whether or not to use them. That means there needs to be two obviously different sets of File menu commands. One that involves versioning, and one that doesn’t. Otherwise the user won’t have a clue when an app supports it.
• Versioning, I would argue, is actually quite common. It’s just that most people do it through informal methods (like appending “-V2″ to file names) that require a lot of mental effort to keep track of things.

• (What the difference between Save As and Save a Copy As are unclear to me.)

  This difference is related to Duplicate. Say you have “File-A” open and have made a bunch of changes. Save As effectively means “take the current state of File-A and let me save it as File-B which is to be opened, returning File-A to its last saved state and closing it.” Whereas Save a Copy As means “take the current state of File-A, duplicate it into a new file which I will name but not open, and keep File-A in its current state.” Save As destroys the changes to File-A. Save a Copy As does not. Duplicate is much like the latter in that the changes to the first file are still present, but could be undone. But an important difference is the copy hasn’t actually been saved. It’s opened as an usaved copy which may or may not be continued as a fork from the first document. Duplicate is actually giving you broader workflow options than either Save As or Save a Copy As.

Command click on the title.

The icon next to the title is actually a proxy for the icon in the finder, so you can, if you wish, use it to drag the file somewhere else (move), or to view it in another app (by dragging the icon to another app’s icon)

Versioning should be in the file system. People shouldn’t lose data if they’ve forgotten to “save” before closing (or, they select the wrong option in a dialog they didn’t read or thought was from a different application).

You admit novices don’t need to go back to previous versions of docs. They they won’t. Then versioning is for advanced users who, honestly, WOULD benefit from versioning at the OS level. And Duplicate pretty much equals Save A Copy.

The problem is simply switching costs for the user, and Apple usually ignores those if they think the benefits are worth it, and they’ve got the success of workflows on iOS to back them on this one.

If there’s one bad point to all of this, it’s this transition period where some-to-most of your apps haven’t been updated for this. You can’t take advantage of this switch when Office ’11 still forces you to Cmd-S constantly.