Does Windows 8 bring in any changes to DirectX (specifically Direct 3D) pipeline?

Windows Vista brought in DirectX 10, thereby breaking compatibility with apps/games which are exclusively designed for DirectX 10.

Does Windows 8 introduce any such APIs, thereby breaking compatibility? I know Metro UI Modern UI apps are one such change, I'm looking at from a 3D Applications/games perspective

To be specific: I'm asking if there are changes to DirectX such that any games/applications "exclusively" targeted at Windows 8 will run on Windows 7.

Windows 8 runs DX 11.1, which is a point release. Anything that runs on DX 11.1 should run on DX11 apparently. The technical details are here but its just way over my head.

Now, this article from the verge is a little more understandable and digestable and along with the above developer notes helps see the bigger picture - the main goals of DX11.1 seem to be performance optimisation and better utilization for general purpose graphics rendering, rather than major changes. Other than the obvious case of ModernUI/winrt applications chances are nothing should break.

MSDN blog says:

Direct3D 11.1 as a common foundation

While adding new features like Direct2D Effects is a great way to help developers deliver new experiences, we also looked at ways to make it easier to use existing DirectX features.

Over years of development, we've added various different features to DirectX. Hardware acceleration of video decoding came alongside programmable shaders in Direct3D 9. In Windows 7, we added Direct2D and built it on top of Direct3D 10. At that time, we also created DirectCompute, a new system for high-performance computation on the GPU that became part of Direct3D 11. One result of all these updates is that DirectX has a very comprehensive set of features around graphics and GPU computation, but as a side effect, it has also become increasingly difficult to create an app that uses video, 2D graphics, 3D graphics, text, and DirectCompute together.

In Windows 8, the new Direct3D 11.1 API is the foundation for hardware acceleration of 2D graphics and text, image processing, 3D graphics and computation, and video. The new API makes it much simpler to mix different types of content in a single scene because that single API now manages all of the GPU resources associated with rendering. This also reduces memory usage by eliminating the redundancy involved in creating multiple graphics device-management objects in app code. In addition, Direct3D 11.1 provides a uniform way for apps to access the various capabilities of different graphics hardware. It provides mechanisms for the app to determine what features are available, and then only uses those capabilities. This enables apps to make maximum use of the GPU’s capabilities, whether the GPU was designed for long battery life on a tablet, or high-end gaming on a desktop PC.

JourneymanGeek's answer is good for the technical details, see the linked pages here and here. I've tried to approach this from the end result angle.
Will games using these features work on windows 7/8?

Regarding new games designed for windows 8 working on windows 7, see the below article:

http://hardocp.com/article/2011/12/22/amd_radeon_hd_7970_video_card_review/

and the relevent quote:

DX11.1 will be in Windows 8 and Microsoft will make a download available to Windows 7 users.

I do not know of the orignal source of that information, however it seems legit.

What we can take from this is that even desktop games/apps that take advantage of new features in DX11.1 will still work providing you download the update to DX on windows 7.

Regarding old games designed for earlier versions of windows working on windows 8, see below:

It appears there are some breaking changes, I've found several reports of older games not working, the site below seeming fairly objective (forgive the colour scheme):

--Dead link removed--

Further info: --Dead link removed--

According to this question: Does Steam Work On Windows 8? steam does work, although not yet officially supported.