I'm sorry but this is just wrong. Duplicating your file involves the same number of steps as Save As. The difference is you do it up front rather than at the end. The reality is either way you choose you are still saving a brand new file under a different name. There is no difference in the number of steps at all.
However, the Duplicate feature does have some obvious benefits over Save As as well as more options.
I think what he might be describing as an extra step is that you
1) go to the menu and click Duplicate
2) wait for the program to duplicate the document on the screen (some apps can take some time at this, I have some big OmniGraffle documents that can take up to 30 seconds or so)
3) go to the menu again and click Save to put the duplicated copy where you want and Save the file to disk.
Instead of doing this for save as
1) go to the menu and click "Save as" to put the saved copy where you want it and it saves to disk.
I'm not debating which method is "better" or more efficient for your work flow, I completely accept that your work flow may be enhanced by the duplicate functionality. However there are some of us that have work flows that flow better using Save As. I think Apple has found a great balance in ML by providing Duplicate as a default method and allowing us to hold down the Option key to change that to "Save As".
For our work flow it isn's so much about having progressive versions of the same document as it is that documents very often get "forked" in their progression, so "Save as" generally is more efficient to do that. If we just needed to see old versions of a document then this discussion wouldn't matter so much to us.
