Well for example.... Win8 and Win8.1 supports DX11.1 and BF4 supports DX11.1, but Win7 only supports DX11.0.
http://www.hardwarepal.com/battlefield-4-benchmark-mp-cpu-gpu-w7-vs-w8-1/11/
The FPS on BF4 with Win8/8.1 is quite noticeable. Sure there are other games out there....
And tell me that's not a deliberate case of throttling back support for Win 7 users in a feeble attempt to get BF4 fans to switch to 8.1.
Microsoft are lower than a submarine's karzi, despicable, rotten and foul.
I will not play their stinking games, they tell me Win 8.1 is their best - it's not!
I have actually been trying Win 8.1 Ultimate 64 Bit, all updates applied with Classic Shell. It's still irritating, though improved on the original pre-release beta I tried all that time ago, I will admit that.
But I still hate it, if I can be bothered, I may post my critique on it but on parting I will just say that the first message that flashes on the start screen after updating is 'You can now buy apps directly from our online store' or words to that effect. Really makes me want to punch somebody.