I'm seeing some pretty heavy load, something like 90-100% on all cores and my temperature maxing out to 84°C!
After a quick look at Task Manager, TrustedInstaller.exe is the cause but what it's really doing is running a setup task for the .NET framework.
I don't mind that Microsoft is doing optimisation on their huge .NET library, but at the same time I would appreciate if it didn't try to cook my hardware while it's at it. I spent quite a pretty penny on my notebook and would like to keep it running for as long as possible.
How Microsoft treats my notebook CPU during updates.
Go to your "Services" manager by typing in "services.msc" into the Start Menu. This will show you a list of services on your system.
Search for the entries beginning with "Microsoft .NET Framework NGEN" and check the status. If it's running, go to it's properties and stop it. An additional but optional step you can take is disabling it.
You should see an instant drop in CPU usage after doing this.