I use Windows 2012r2. Some minor changes compared to 2008, but, for the most part if you used 2008 2012 will be no problem.
Things that work much better are compression and cache. I had strange results using built in IIS compression and output cache with 2008. Now it works as expected and really does decrease server load. I use both kernel mode and file cache.
Can I ask what your page generation times are like when using Windows 2012? I'm having big problems trying to get XF running as fast as it should on IIS 8.5 when compared to my test machine.