The constant churn is frustrating. Since Vista almost every release has had vast sweeping UI changes, and it just feels so pointless.
To me, the perfect example is the MS office icons - in 7, MS dropped the text-labels off the taskbar entries. This would make sense if they had any kind of consistency, but MS office has had a complete makeover with every release, not even sporting a consistent color-scheme.
Major new releases are hardly inappropriate. There's still a lot of change in computers. Recall XP had no wireless support until SP2, and it hasn't been until Win7 or so that SSD's have been handled optimally (TRIM and so forth)
There really haven't been many major changes to the x86 architecture since the 386, with the notable exception of 64-bit recently. Pretty much everything else should be handled with driver updates or at worst a service pack.
I wouldn't even object to paying for those kinds of upgrades, if I needed them, if I could take them without getting a bunch of unwanted tinkering with the UI and toolset.
I eventually gave up on Windows as my primary OS because of many small, incremental breakages like changes to the batch language (without really fixing any of its serious shortcomings), it becoming impossible to do a simple file search from Explorer, then it becoming impossible to change file associations without a 3rd-party tool. But hey, if you want an animated dog for no reason, that's no problem!
I still need Windows 7 for some things (3D software is still almost exclusively Windows-only) and I still find certain things about OS X a bit clunky, but overall I'm rather happy that I no longer have to care about what Microsoft might mess up in Windows 9.
There really haven't been many major changes to the x86 architecture since the 386
CPU architecture is hardly all that matters to the core OS
Pretty much everything else should be handled with driver updates or at worst a service pack.
Driver updates work fine for adding support for a new model of graphics card, but when you introduce a whole new kind of device (e.g. WiFi, SSD) the implications reach into the OS itself. They managed WiFi in a service pack for XP, but it was both a pretty unprecedented level of change for a service pack, and always felt kind of tacked-on.
Oh, I forgot to mention threading in my other comment. Windows 7 was the first time the OS seemed to do a good job of both scheduling userspace AND core OS functions across N cores. I'm guessing that would be outside of the scope of a service pack.
As long as OEMs pre-install Windows, and ISVs make binaries for Windows, people will "buy"* and use Windows. But times are changing. Consumers don't upgrade PCs as often as they used to, or they switch most home use to tablets. And most software used by consumers these days are web applications.
Anecdote: I'm a software engineer who develops using Windows. But at home I rarely turn on a computer. I do most everything from my iPad. Though to be fair I often do most of my digital errands from work on my PC.
* Most consumers never directly pay for a Windows, or any OS really. They get whatever the hardware vendor installs.
How long can these guys go on releasing new operating systems? And how long will people keep buying them?