So, as much as this announcement sounds unnecessary at best, if another part of my job needs me back on Windows 10 someday, I may come back to this.
I have seen nearly no software that doesn't work in a backwards compatible way on windows. Tha's the thing microsoft does best of all.
What was it that became incompatible with Win8 that meant a piece of software that installed on Win7 now wouldn't install?
The last app that stopped working for me was some 16bit vb apps I had but those run just fine in a virtual 32bit XP I can fire up (and in the "xp mode" when that was availble).
I think the most notable example of this was some time zone handling bug in The Sims 3, that made that game unplayable with Wine if you were in certain time zones. The problem was that Windows XP didn't actually report DST information correctly to the version of Mono embedded in it, and the Mono devs dealt with it by basically not validating the value returned from XP. So Mono would crash when it got correct time zone information from Wine and from later versions of Windows, thus crashing Sims 3.
Looking at their bugzilla for the issue, it seems as if someone went through and deleted old comments. There were many whiners demanding that Wine fix something that they didn't break. https://bugs.winehq.org/show_bug.cgi?id=18991#c43
Obviously any developer can screw up and do thigs like "if !winVersion.StartsWith(...)" and there is not much microsoft can do about that, apart from naming windows 9 windows 10...
But even broken and buggy API's tend to be maintained by microsoft just because they can't test all the software floating around that depends on it. So it's usually very very hard to accidentally make a program run on Windows version N but not on Windows Version N+1
It used to be that when Microsoft found that a specific program was getting in the way of a bugfix, they'd detect the program and perform the buggy behaviour, or they'd patch the software on-the-fly. I have no idea if they still do this.
I'm very happy even with terrible bluetooth support in comparison to Windows. I couldn't get a Logitech mouse to pair with the Dell XPS Developer edition. Tried all the command line tricks with bluetoothctl and hcitool. I plugged in a really cheap Kinivo USB bluetooth dongle I had laying around from a headset and it worked easily. Go figure.