My steps (after backing up everything before deleting it):
1. Uninstalled VS2012 Pro from Windows 8 64 bit
2. Removed the following registry entries:
HKEY_USERS\.DEFAULT\Software\Microsoft\VisualStudio\11.0; HKEY_USERS\.DEFAULT\Software\Microsoft\VisualStudio\11.0_Config; HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\VisualStudio\11.0; HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\VisualStudio\11.0_Config; HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\11.0; HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\11.0_Config;
Note that I did not delete or clean up HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\VisualStudio\11.0 which contained the license key
3. Deleted the following directories:
C:\ProgramData\Microsoft\VisualStudio\11.0;
C:\Program Files (x86)\Microsoft Visual Studio 11.0;
C:\Users\UserName\Documents\Visual Studio 2012; C:\Users\UserName\AppData\Local\Microsoft\VisualStudio\11.0; C:\Users\UserName\AppData\Roaming\Microsoft\VisualStudio\11.0
4. Renamed a .Addin file in C:\Users\UserName\AppData\Roaming\Microsoft\MSEnvShared\Addins to stop it loading.
5. Installed VS2012 Update 1 from an ISO (ex MSDN download), carefully choosing not to try to import settings from VS2010. Did not install patch_KB2781514.
6. Installed VS2012.2 from an ISO