The Start Screen made a few critical improvements to the Start Menu, it just had the misfortune of being bundled with Metro.
Namely, it eliminated a few problems caused by third-party developers cluttering up the Start Menu with extraneous folders and shortcuts (no more nested folders). Now you can have a better organized Start Screen but still have access to all those extra shortcuts if you need them.
Bringing these enhancements back to the desktop would certainly be welcome, at least by me. Also, IIRC Tiles support was already announced for the Windows 9 Start Menu. So, like Android widgets or the already-existing desktop Gadgets... could be useful. I probably won't use them, though, except maybe for the weather.