Honestly, I've been running Windows 8 ever since the first preview. Granted I was dual booting at the time with Windows 7. I hated the lack of the Windows 7 start menu, at first, but after a time I learned keyboard shortcuts that had me flipping back and forth. I love the quick glance ability of the Metro Screen, quickly check my sports, weather, email and facebook and then swap back to the good old desktop. There are plenty of free programs to make your system fire up and run EXACTLY like Windows 7, so with that little issue that most people have out of the way. Windows 8 uses far less memory (700MB everything loaded versus 1.2GB that 7 used on my rig) It utilises AMDs funny core structure (anything based off Bulldozer including Trinity, Steamroller etc) better than Windows 7, handles networking better (I had a 10ms ping decrease to most of my Battlefield 3 servers) increased framerates (10-15fps in Battlefield 3, 5-10fps in most others) more stable on overclocked rigs (I was able to push my CPU to 5.0Ghz, sadly the heat wouldn't allow me to keep it there) and there is also the lovely DX 11.2 (I hate MS for doing stuff like this, there is no legitimate reason that 7 cannot handle 11.2) The biggest gripe anyone has is "the tablet interface", "the phone style desktop" etc etc... 90%* of these folks haven't even tried the damn thing, and feed off the internet hate machine.
Long of the short of it is, Windows 8/8.1 performs extremely well for gaming. The biggest gripe most people have is the Metro interface, which is quite honestly easily (and freely) turned down or completely off. Leaving you with what feels like a far more optimised version of Windows 7.
Make your Windows 8.1 look and feel like Windows 7 but keep all the Windows 8 upgrades for FREE with: http://www.iobit.com/iobitstartmenu8.php
*95% of all stats are made up on the spot.
Desktop: FX8350 @4.7Ghz, Gigabyte 990FXA-UD7 Motherboard, 16GB Corsair Vengeance @1.7Ghz, Dual Asus R9 290X DCU2 @ 1.1Ghz, Kingston HyperX & V300 128GB SSDs, 4TB HDD, CM Inferno Gaming Mouse, Logitech G510, 3x Acer 223W Monitors@5040x1060, Antec DF-85, Corsair H100i, Corsair HX1050 PSU.
Laptop: MSI GX70: AMD A10-5750 @3.5Ghz, HD8970M @1.1Ghz, 16GB Corsair Vengeance @1.6Ghz, 250GB Kingston HyperX SSD, 1TB SSHD, 750GB Seagate, Gamdias Demeter Gaming Mouse, CM SF-17 Cooler.