Well I did it.
Not that I would recommend it but I decided to upgrade to Windows 8. Short take would I do it again? Sure. Did I gain anything? See below. Did I run into an issue or two? Sure. However several hours later it's upgraded and back to performing its duties as good or better than ever.
The PC is used 100% for WMC, XBMC and a few related apps such as Hulu Desktop. Which means there is nothing on the PC that I worry about such as needing to be backed up beforehand. I would recommend cloning your drive beforehand so you could punt at any time. You could use the free Partition Wizard I linked to in the first post.
I downloaded and ran the Upgrade Assistant and it blessed most of the drivers and apps (all that I cared about) stating they would be fine with Windows 8. So I purchased my license (at the recent PC purchase price of $15) and downloaded Windows 8. As I did with my other PC I had the Upgrade Assistant burn the software to a DVD electing not to do an existing upgrade. Typically, I like to start fresh as it feels cleaner (although often offers further challenges). Once I had my license and DVD I booted off of it and was at the point of no return. I deleted my partition and created two (created an additional partition to store all data - recordings, etc.) and Windows 8 did its thing. I have always been impressed how fast it installs not that it matters...
Installation was painless and my wireless keyboard and Harmony still worked. Video was 1080p so it looked like I was good to go. I ran Windows Update which installed a few hundred Megs and then installed Media Center. My key worked like a champ and almost instantly I was left with now let's make it work...
Media Center being identical wasn't a challenge to configure and Dolby Digital worked. My only issue configuring WMC is I have a local channel that broadcasts on two frequencies and WMC uses the low power channel so I have to manually add the correct channel. It only took a few minutes to scan the guide and add back my 30 or so Series recordings (right clicking on the show speeds up the process). Just be sure to update your recording defaults beforehand (I only record new airings).
With WMC up and running (bare bones) I decided to install XBMC and I noticed my sound card (AV receiver) didn't list HD audio as being supported. I found Windows had installed a Microsoft driver for my i3 chip so I had to download/install Intel's HD Video/Audio driver. Then I installed the Shark audio codecs for Windows 8 and they require only two changes to work (set to bitstream and 64bit).
After a little configuration XBMC (12.0 RC3 with Add-ons) was working like a champ. By this time I noticed the PC was a little faster at everything. Not overly so but enough it was noticeable regardless of what I was doing. At this point I had a working bare bones version of WMC and XBMC and I knew I wouldn't be going back. It was down to getting my tweaks working and making Windows 8 work the best in my appliance environment. I also noticed my image was improved (more on that later).
First thing I did was enable auto log-in (configured identically as in Windows 7). Now I was presented with the (new) Start screen. I have read several ways of bypassing it. Most often by simply scheduling a task to run at log-in. Playing around I noticed my Harmony's directional keys work perfectly with the Start screen so I tweaked my Tiles until my heart's content and ended up with a nice looking and easy to use front-end. One concern I had going in resolved nicely.
Now I was down to the little things that make the day to day usage more valuable and I was hoping they would be resolved as easily. Hulu Desktop worked great even though if I remember correctly the Upgrade Assistant stated there would be an issue. XBMC and Hulu worked great being called by WMC. Then I hit my first road block. That being ESPN which I believe uses Flash for video. From what I found out Flash was installed by Internet TV and since it has been discontinued there is no way to install it for WMC. ESPN plays fine in my browser and it's not exactly a big loss as it was rather funky inside of WMC but it's a loss. It's also available via XBMC.
The PC still hibernates with the Xbox 360 waking it. The custom programmed keys on my Harmony still work such as starting and closing WMC. At this point I was back to where I was with Windows 7 with one obvious difference. I kept noticing my image had more contrast. Similar to if I had installed a Darlet (increased contrast). It isn't overblown rather it just gives the image a greater 3D look. I found this rather strange since I think the video drivers (Intel HD2000) is the same for Windows 7 and 8 and I'm using the same settings. However I noticed overscan (the PC's not an app's) is a little different (of which you don't have control over) so obviously there is a difference. Turns out this change was worth the upgrade... who would have guessed.
The external Blu-ray driver still works (had to install from disc)
HDHomeRun works as expected
Looking at Themes and I didn't find one I loved and ended up using High Contrast Black - it's rather retro and for some reason feels like a fit (for HTPC/appliance)
To recap I am more than happy since my new image makes it appear I have a brand new TV. What more could I ask for! I found it rather funny after spending most of Friday night upgrading Saturday in the mail is my rebate check from HP for my first Windows 8 upgrade... it must have been destiny.
A few hours
Flash for WMC (ESPN)