I just upgraded my Windows 7 installation to Windows 8 Enterprise RTM. The compatibility check failed because of Intel PRO Wireless Utility and Avira AntiVir Pro. After uninstalling the both programs the upgrade started regulary. After some reboots and 1,5 hours installing I logged in first.
Everything looked fine, all apllications started as usual. The desktop and taskbar symbols appeared as before, just the start button was missing. I installed the ClassicShell and got my start button back.
In combination with ClassicShell Windows 8 has nearly the same usability as Windows 7 + the possibilty tu use the new features and the new (formerly known as METRO) interface. So I wish you a happy upgrading and installing 🙂