More generally, Apple was providing working OS upgrades for years while the notion of upgrading Windows between major versions was basically laughable. Wasn't Windows 8 the first version of Windows that you could actually upgrade to and have the system boot successfully? Maybe Vista to 7 worked for people. I never bothered trying. But I remember upgrading from OS X 10.3 to 10.4 and being floored when everything just worked.
If older editions of Windows just forcibly purged all the drivers when you upgraded, and told you to reinstall them afresh from the installation CD/OEM site (where you'd then get a version that's maybe for your current OS instead), that could have saved everyone quite a few headaches.
Then again, with major peripherals (displays, keyboards/mice, Ethernet cards, USB controllers) being much less standard than today, ripping out the OEM's driver could wedge your computer.
i have upgraded (or my dad had anyways) from win 3.11 to win 95 and win 95 to 98. i think i clean installed win xp when i got a new computer but eventually i upgraded that to win 7.
all of them ran fine. or was that just not the norm?
What iOS 10.3 did was basically the equivalent of having a Windows upgrade which converted FAT/FAT32 to NTFS in-place without the user having to manage the process.
I wonder if Apple will take the same approach for macOS (convert manually if you want for now, or we'll use it if you reinstall). Seems like a far greater risk for Apple if upgrading the OS breaks something for a lot of people, when they want users to be completely comfortable about updates.
It definitely worked on the boot partition at least on XP, not sure about 2k. If it can’t lock the drive it schedules it to be done at boot time (similar to on-boot chkdsk).
I think my failure rate got to about 30% before I stopped even trying to run the upgrade and just did a fresh install after backing everything up.