One of my pet peeves with Mac OS X always appears when I'm in the process of opening a file from an app and want to either make a duplicate of an original or just want to rename the file. With Lion and previous versions of OS X, that meant that I'd have to close the "Open" dialog, open a Finder window, make the name change, and then go back to the dialog. AppleInsider noted today that the Mountain Lion developer preview adds some changes that will eliminate this pesky issue.
Mountain Lion now includes "new and improved" Save and Open dialogs (see above) that finally let users rename files from the dialog -- no trip to the Finder required. With a double-click on the name, it becomes editable in the dialogs, exactly what you see in the Finder now.
Files can also be renamed from the title bar of apps. The Versions pulldown currently displays options to lock, duplicate, revert to last saved version, or browse all versions. In Mountain Lion (below), the pulldown is changed so that it now adds Rename, Move to iCloud, and Move To items.
While this is just a small change to the operating system, it's something that a lot of us have wanted for a long time.