Debian. Vista. And somewhere around Snow Leopard, though I stopped getting upgrades around that time so fuck you apple.
These are the selections of the peak power user, and they shall not be questioned, as the punishment is using Windows 8 for a month, followed by death, which will be merciful after that month.
I always think that Vista was alright, it just took a bullet for every version of Windows that followed. It introduced overdue changes to many long-standing Windows conventions, changes that still stand now. If Windows 7 had been the next one after XP then everyone would have hated that instead.
Another issue was that Vista had very steep system requirements, which Microsoft deliberately understated. As a result it ran like shit on a ton of machines despite them technically meeting the requirements.
But yes, I do agree, 8.1 was great, a lot better than 10. The problem with it was the start menu (easily fixable) and the fact that MS didn't invest money or time in it after 10 came out, so a lot of bugs went unfixed.
It was way too early. If that happened after 11, very few would mind. But it happened way too early. 7 had the classic 6.x kernel start menu, and 8 suddenly had... no start menu button at all 😬. That was their mistake, way too much change way too early.
i never liked the inconsistent window management though.
On 8, (i dont remember for 8.1) there were some apps and menus that forced "tablet mode" and could only be interacted with in fullscreen. Other applications would open in what looked like tablet mode by default but you could break them out into desktop mode, after which they behaved normally.