Every computer in this house has Windows on it, even my macs for work have a bootcamp partition with Windows 7 Pro. They also all are Windows 7 despite the fact that I have no less than 5 free copies of Windows 8 from work or developers conferences/seminars.
I remember being at those conferences and all the programmers and developers saying the something: we understand the logic behind having a unified UI across every platform....but the problem is every platform is different in terms of interface. Although I think part of the situation was that MS was expecting that all PC's moving forward would be sold with touch screens whether they were laptops or desktops. Which increasingly I'm seeing more and more all in one desktops with touch screens and tablet/notebook hybrids. Touch interface is great for tablets and phones. Not so much for desktops though. I saw this working for a company that wrote point of sale software. Initially we had a lot of users that had touch screens and on their next round of updates actually went to standard monitors and then keyboard/mouse for input.
At least Apple has stuck with having OSX & iOS as separate operating systems. It's true under the hood they share a lot of the same code, but their UI's are optimized for different input methods. Apple introduced launchpad giving OSX a iOS like App launcher, but you have to click an icon or button on the keyboard to bring it up. They haven't changed how OSX is used much in a decade.
Likewise, many people have now in business are used to the start button because that's what they have used for 15 going on 20 years. Hell there are kids entering college who never knew using a computer without a start button. The big mistake Microsoft made was wholesale change. It takes a lot of time to retrain people in the business world when you go messing with the basic UI.
If Microsoft had left windows 8 with a standard UI with start button and then a "Metro launcher" like Launchpad making it optional to bring up the tiles to get people used to it and then eventually transitioned to the new UI over 9/10 there would have been a lot less fussing.