Windows Mess
Windows OS is a mess.
Microsoft's just released its November rollup of product fixes to address issues that go back to April 2014. The new dump includes patches galore for Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2. The latter gets some handy fixes, such as one that includes “performance and reliability improvements in the cluster, …
I assume that's a relative statement... but no idea what against.
The fact of the matter is that all of the OSes are really a bit of a mess. Mind you, it's all a bit sodding complicated these days too.
Win Server at the very least seems anything but a mess if you're actually having to run infrastructure with it - it's far less of a mess than the Linux variants in our experience. YMMV of course...