I guess the standard one word response of 'farewell' is appropriate ;-)
I never understand when people moan about a lack of new features to the OS though. What do you want it to do? I'd prefer them to be taking things away, rather than adding them, making it as quick and stable as is possible (whilst providing a very limited number of applications which are ultimately required for multi-device/data integration)
Any other apps, should be distributed as such and require me to install them rather than remove them or live with them being unused.
I use macOS and Windows daily, and feel there's very little the choose between them in most cases, other than a different approach. The Windows 7 machine I use at work is just as stable as the MacBook or iMac I use at home, and whilst my preference is still macOS, it wouldn't be a problem to switch either way. The applications present a slightly different challenge, with some of the Windows versions working better than the macOS ones (Office 365) and some of the macOS ones not available on Windows (OmniFocus, Aperture).
Heck, for something's, you'd be better of without either Windows or macOS and using a Linux variant or even FreeBSD.
I think the hardware argument makes a lot more sense, but then you just buy what you can afford and what best fits your requirements and find the appropriate forum for information and support. Not sure why you'd need to announce your arrival or departure to either