Combine the Menu Bar and Title bar.
Remove the word "Start" on the Start Screen and move the user profile icon to the side/bottom for landscape/portrait mode.
Tabs (or buttons with optional icons?) for Explorer.
Customizable buttons like VLC's customizable window interface, basic, advanced, and arrangeable buttons for Explorer and/or other applications.
Mouse Gestures, proper implementation of "Grab And Drag" for background space. QTTabBar's double-click background space option.
More Options/Adjustable taskbar (add, remove, arrange options, weather, headlines, stocks, a tab for auto-hide, the recycle bin optional). Maybe have the (customizable) options of the Charms Bar in the taskbar?
Metro apps could be windowed and at least have an option to change to the Desktop color scheme (light greys and light blues). And for the windowed mode, they already have a landscape or portrait setting, just choose one as the default for Desktop and let us have it windowed (along with a Menu bar.)
THE START BUTTON SHOULD NOT DISAPPEAR.
Metro applications should NOT have second taskbar on the left. They should be located in the original taskbar.
The scroll bar for the Metro Start Screen should NOT be at the bottom of the screen. It should be a lot smaller and right underneath the menu options. Maybe a small bar that has a glow that tracks from left to right as you scroll?
Full-Screen Metro apps should NOT have cut off pages (like the weather app) and should be appropriated for landscape/portrait.
The side bar should NOT cover the taskbar and should have some kind of border.
When using the side bar for search, A Desktop browser window should be optional, instead of, opening a full-screen Metro app. (And an option for Google instead of Bing.)
IE could give top headlines for a live tile (widget.)
There needs to be a Desktop version of Messaging, Photos, and Contacts.
DeviantArt themes on the Windows Store.