The problem is that "Save As" has a very specific meaning that Apple's new implementation doesn't respect. In every other DE / other OS X applications / prior versions of OS X, "Save as" means "take the current working copy and save to disk under the given name, presevering the original". In Mountain Lion, "Save As" basically means "Rename". If Apple called the feature "Rename", this wouldn't be an issue; it's an issue because Apple co-opted a very well-established term for a completely different function