It'd be really nice if there was the option of making "Save As" open a new tab with the new file and keep the previous version intact (for example if you have one file and are making a new one based on it).
I tend to create duplicate pages all the time for static sites this way, but every time I do it I have to open up the old file again after using "Save As" so I can continue working on it along with the new one.
To me this seems more logical from a workflow perspective, anyway.