To dispel some rumors:
Currently, Windows 10 performs WORSE than both 8.1 and 7. It's not a significant margin, but everyone saying that 10 runs better is essentially wrong.
This article shows a bunch of benchmark, the aggregate for games is 8.1 > 7 > 10.
http://www.ocaholic.ch/modules/smartsection/item.php?itemid=1460&page=12
EDIT, DISCARD THIS. I just noticed the article is very old. Still looking for actual comparisons on release version, since I can't find so many of them...
Other articles all reliably show worse Windows 10 performance on CPU physics tests.
On top of that boot times are very slightly longer, and memory footprint is similar to 8.1, but still larger, and so less optimized.
So, in all key areas: loading speed, memory footprint and game performance Windows 10 is simply worse that those preceding it.
And I wouldn't be surprised if the marginally worse performance across the board is due to all the tracking and spywork that Microsoft has layered on top of the OS.
Basically Windows 10 is Windows 8.1 plus a bunch of tracking/spy applications on top of it.
I wish the numbers showed at least some small improvements, instead of things getting worse. What's even the point?