I've been running the Windows 8 Consumer Preview for a few months and although I'm okay with Metro replacing the Start Menu, I hate seeing the new interface by default every time I reboot. When Windows 7 starts, you hit a login screen (assuming it's enabled) and then you're brought straight to the desktop.
When Windows 8 starts, it displays a lock screen that you have to move out of the way before entering your credentials, and then you have to dismiss the Metro interface before accessing the desktop. Like I said, I'm cool with Metro, but I have no desire to see a full-screen Start Menu when I log into my PC. Read more at TechSpot.