Well - live dangerously and get what you deserve I suppose, but I upgraded my main machine to Windows 8.1 today thinking (naively) "it's adding some bells & whistles, should be fine".
Since upgrade though, Steam is generally in trouble. Skyrim CTD, X-com won't start, and Tomb Raiders frame rate has dropped to a crawl.
Also - I can't get nexus mod manager to start either (even re-installed it, no joy).
Will try some things tonight, but wanted to forewarn other adventurous types... I used to be an adventurer like you, but then I took windows 8.1 in the knee... :-(
If you're having a better experience or have fixed it, please let me know here..