If you like keeping current with your DirectX version and happen to dislike Windows 8, you're going to be finding yourself in a bit of a bind. Despite having shipped alongside Windows 8, DirectX 11.1 hasn't been talked about too much. In fact, it wasn't until just now that I even learned of it. Being a minor version increase, however, nothing here is truly major, leading to a very confusing and disappointing choice by Microsoft: 11.1 is exclusive to Windows 8.
This comes as a bit of a shock to me, because about a week ago, I defended Microsoft in a conversation stating that it's "unlikely" that the company would come along and release a piece of integral tech and keep it exclusive to Windows 8. Little did I realize it already happened; it just took a little while for people other than game developers to learn about it.
S.T.A.L.K.E.R.: Call of Pripyat - DirectX 10 (Left) vs. 11 (Right)
The biggest feature 11.1 introduces is native stereoscopic 3D support. This is pretty big, because as it stands, current games that best support 3D must be designed with both NVIDIA and AMD in mind, or one over the other as has become the case many times. With native support, it means game developers can create a stereoscopic game without worrying about vendor-specific APIs.
A full features list can be found here, although it helps to be a developer if you want to understand any of it. The admission by Microsoft on 11.1's Windows 8 exclusivity took place on the Visual Studio forums where Microsoft's Daniel Moth said:
"DirectX 11.1 is part of Windows 8, just like DirectX 11 was part of Windows 7. DirectX 11 was made available for Vista (bing it), but at this point there is no plan for DirectX 11.1 to be made available on Windows 7."
Even if you have no interest in anything DirectX 11.1 offers, this definitely feels like a burn. It's not as though Windows 7 is "outdated" by any stretch, and it's in fact what a lot of people would consider perfect (as far as OSes go). Couple this with the fact that Windows 7 won't be seeing a Service Pack 2, it seems likely that this is the new trend we can expect from Microsoft anytime a new Windows version is released.