Here's a video of VMWare Tools upgrade in Windows 8 x64 that demonstrates how I'm logged off - you can clearly see (around 4:50) that I'm kicked to the logon screen, and that I have to log back in (and then repair VMWare Tools install). I have repeated this several times, and only once the VMWare Tools upgrade finished properly on the first try.
The Files in Use page of the installer is completely useless, both because the same thing happens regardless of which option you choose, and because those services have to be stopped anyway.
Host is Windows 8 x64.