I did a clean install, and after it completed I went to the Nvidia site and downloaded the latest drivers and software for my graphics card. When the system restarted it wouldn't load the desktop, it just looped. I figured I'd boot into Safe Mode to roll back the driver but neither f8 nor Shift + f8 would work. Weird...
The next thing I tried was booting to the Win8 Pro disc I made from the ISO (and installed with) to try a repair but my PC would not boot to the disc. REALLY weird....
I'm replying to myself because I learned something valuable about Win8 and my media center PC this weekend that might help others.
I decided to swap out the nVidia 210 back to the original ATI 4350 (the 210 is headed to a friend's build) so I went through the standard drill: uninstall card and drivers in Device Manager, shut down, etc. After rebooting and updating the ATI drivers I noticed I still had the nVidia drivers in the uninstall app, and they refused to be removed. After futxing with it for a while I decided to try Win8's "refresh" option for the first time, but that meant booting to the Win8 disc and I had trouble with that before.
This is what I discovered:
1. I wasn't waiting long enough for the disc to boot. With a modestly powered system it takes seemingly forever to get to repair mode but if you're patient it will appear;
2. Refresh works great, your files are preserved, but it uninstalls everything, including all the updates. However, you do end up with a nice clean install;
3. ATI's latest Win8 drivers work sweet with my TV. I didn't have to play around with over/underscan to get the desktop's resolution correct, the proper resolution was set by default.
I was never really happy with the upgrade because I suspected there were glitches hiding in the background but now I am, everything is running like it should be.