From what I read, it sounded like as it existed in Windows 8.1 the UI/UX was too complicated/confusing for users at the time and they were removing it until they solved some of the UI/UX problems.
It does look the UI has evolved (a dedicated column in Details view, some new clues in the command line even; in the demo the DIR showed the file size in parentheses, presumably to note a placeholder).
It also sounds like the UX has evolved with things like file prediction to predict some of the files to load/unload from a device.
