I remember the early days of XP weren't all that rosy, it was generally regarded among people I knoew as a slower version of win2K with a fisher-price interface, support for DOS games that while marginally better than 2K was still absoloute crap compared to 9x and a new online activation system that could deny legitimate users use of their software and make life harder for computer repair guys while having very little implact on pirates (who just use the vlk version that didn't require activation).
On the plus side 2K and XP were a lot more stable than 9x and seemed to solve the issues of running out of windows reousrces when having large numbers of windows open.
XP SP2 was also a mixed blessing, on the one hand it fixed some security issues that really needed fixing, OTOH it did break software (I remember having to upgrade nero to get CD burning working again) and massively change the way certain things (notiablly the firewall) worked.
XP aged pretty well though, the glitches were worked out, games moved from DOS to native windows and hardware improvements mostly eliminated the performance concerns*. so by the time vista came along the comparision was very much XP good vista bad.
Win7 to me was "I guess the performance isn't as bad as vista but why the fuck did they coop the all-programs menu up in a small box and group windows on the taskbar in a way that made it much harder to remember which was which". I avoided it for as long as I reaosnablly could but eventually hardware support, the impending end of security updates and for personal machines the fact that manufacturers generally didn't offer XP proffesional x64 edition as an option forced my hand.
I've only briefly used 8 and 8.1 but my impression was very mucha schitsophrenic POS that couldn't decide if it wasnted to be a desktop OS or a tablet one..
(3.11, good, 95, bad, 98, good, ME, bad, XP, good, etc).
The only real difference I noticed between 95 OSR2 with windows desktop update (I did regard windows deskotp update as a big improvement) and 98 was USB support (in theory the last versions of windows 95 had USB support, in practice there didn't seem to be any drivers available), the only real difference I noticed between original 95 and OSR2 was fat32 support. I remember 95 being a big improvement over 3.x but admittedly I hadn't been using PCs for very long when we upgraded (our first PC came with 3.1 installed but came with a free upgrade to 95) and i'm sure my opinion would have been different if I'd tried to run 95 on a 386.
* My theory was that developers optimised their software until it ran tolerablly on their own hardware, so it ran like crap on low end hardware at the time of release, acceptablly on high end hardware at the time of release and great on hardware released a few years after the software was.