Although I'm not a big fan of Windows 8, I had to replace one of our dedicated servers at Hetzner and decided to go with Windows Server 2012 (at the same time, making sure our applications are 100% compatible). So we now have one on 2008R2 and one on 2012. When I find myself working on our 2008 server and thinking "I wish this server was loaded with Windows 2012", then I'll consider upgrading my desktop OS to Windows 8.
I installed Windows 8 a while ago. Must say that I am enjoying my time on it. So far I have no issues with it. The App store is not that great though.
But where Win8 shines is on a tablet. At work we have a few Win8 tablets, and they work beautifully. You then all of a sudden realise what the thinking was behind the MetroUI.