Not the biggest fan of 8 series, but the best thing about it was some of the energy optimisations - as they were going to target mobile. The kernel hibernation is good, for quicker start up. But sadly that's at the expense of hibernating proper.

8.1 brought back things like the closing button on metro apps, and some other fudging, to make it a bit more Win 7, and it just felt like even more of an abomination. The control panel/metro settings mixed UI - is the thing that killed Windows for me. In Windows 10, I can't find anything setting wise particularly easily. And on a recent new laptop start up, I cringed at all the options that I had to turn off, and at the apps I tried to remove.

Here's unpopular opinion: start menu really did need a remake and I like the designs 8.1 had compared to 10. Also, IIRC 8 has some optimizations (including some tweaks to better support ssds).