CU2 for SQLServer 2012 SP1 is one key update which you should review and deploy if found necessary. I have found this very much needed for all my SQL2012 SP1 deployments. This CU contains a very important fix(KB2793634).
Note – The choice to deploy CU2 or just the fix (KB2793634) depends on your environment needs.
Here is why you need this fix –
As soon as you deploy SP1 for SQL2012 the Windows Installer (Msiexec.exe) process is repeatedly started to repair certain assemblies. Additionally, the following events are logged in the Application log:
EventId: 1004 Source: MsiInstaller Description: Detection of product ‘{A7037EB2-F953-4B12-B843-195F4D988DA1}’, feature ‘SQL_Tools_Ans’, Component ‘{0CECE655-2A0F-4593-AF4B-EFC31D622982}’ failed. The resource”does not exist.
EventId: 1001 Source: MsiInstaller Description: Detection of product ‘{A7037EB2-F953-4B12-B843-195F4D988DA1}’, feature ‘SQL_Tools_Ans’ failed during request for component ‘{6E985C15-8B6D-413D-B456-4F624D9C11C2}’
Source – http://support.microsoft.com/kb/2793634
Here are the screenshots of the application log. These are shown as warnings, and could easily be missed.
When this occurs there is a spike in CPU.
This process is repeated every 2 minutes and can cause heavy registry usage issues.
Registry issues can cause multiple failures and a sample one is
Note – Again, this varies from environment to environment.
Conclusion
Deploying the fix or the CU will resolve the issues related to the installer process.
Thanks for reading and keep watching this space for more.
SQLSailor 
This bug is so bad that this patch should have been a part of a Microsoft update.
when I was hit with the bug It took a few weeks buy my registry to fill silently in the background. Once full, my profile would not load when logging on, i could neither uninstall nor repair SQL and so many other problems. Even after paying MS for support to help with repairing my computer the ultimate resolution was to restore a registry backup i had made 3 months earlier. Luckily the only change i had made since then was installing SQL 2012.
Very true,this is a real bad bug. We almost reached your situation but one of my collegue was smart enough to catch this one at the right time.