Windows itself isn't bad, but the driver ecosystem is completely rotten. Any muppet with a code signing certificate is apparently capable of writing driver code that gets injected into the kernel.

But this isn't a problem if you buy quality hardware?

Yes. It's often the case that a good motherboard will have some super generic driver either for the ethernet component or the on-board audio chip.

It's truly astonishing how bad it is even with big name vendors like Asus.

I've had various issues on two separate clean installs of Windows 10 in the last two weeks, one of which was the start menu being broken, and the user profile being damaged to the point where I had to do a full reinstall. Official App Store apps don't install for various reasons (Onedrive) or become damaged etc.

I guess this may be a case of 'grass being greener' as suggested by someone else in this thread. I just don't seem to remember having any of these issues on my 2010 Macbook Pro running El Capitan. Then again, this is purely anecdotal.

Win 10 is pretty stable, but I for one had all kinds of issues when it just installed the Anniversary Update on it's own. I couldn't use my start menu without the computer locking up for about a minute. Spent a few hours researching it, tried multiple fixes which didn't work.