Nope nope nope.
Microsoft should bring back the Start button on the desktop AND add the start button in Metro, at least on devices (i.e. non-tablets) that don't have a hardware Start button on the screen bezel.
No matter how hard Microsoft tries to educate, users won't like having to deal with a non-visible UI element, particularly one so crucial as the Start button. Gestures are great for interacting with stuff that's already on screen, but totally unnatural for bringing up interface elements out of nowhere.
Yes, it's very bad that the Start button comes and goes from the screen, but that's a reason to ADD it in Metro, not a reason to hide it from the Desktop.
