The fact is, it really didn't work for Apple. Short of a few common design choices, iOS and OSX are very different, and for a good reason. I am not sure why it's not obvious to people. Mouse or keyboard driven UI can be much smaller and tighter, with a lot less chrome, to allow more room for data. Touch UI has to be chunkier by default. The simple truth is Metro UI works amazing on a touch device, I love it. Windows 7 works just fine on PC. What Microsoft really needed is 2 separate operating systems, just like apple. The Windows line could have been updated with a fresh skin, more stability improvements, and some core new features here and there. The Metro OS could have been a separate OS for the Phone, Tablet, and TV markets. Instead Microsoft now has 4 incompatible OS lines which all function very different, but look identical, only adding to the confusion:
1. Windows 8 - For PCs, Tablets, and God knows what else,
2. Windows RT - For Tablets which are not as nice as the Windows 8 tablets but can run some of the same software, but not all of it, and some apps which work on the RT actually do not run on Windows 8 tablets, and, so ..... yeah.
3. Windows Phone 8 - Exclusively for phones. For convenience, incompatible with Windows Phone 7 and 7.5.
4. XBox OS - Runs only on XBox, looks like Windows 8, but works very different.
So, instead of 2 visually distinct operating systems, Microsoft now has 4 visually similar operating systems. I can see their logic, they wanted to leverage their huge PC instal base to drag some users to their Tablet and Phone products. Much like Apple is using iPods to sell people on iPhones and iPads, and perhaps later, Macs. But the problem is, they are not really achieving that goal, while pissing of their core PC customers.