The recently introduced Xinput support is obviously taken from the 360 client (button mappings are fixed).
This got me thinking that it might be possible for SE to reuse the D3D9 code from the Xbox client as well.
And it HAS to be D3D9, the 360 does not have any backwards compatibility with previous versions of DirectX because it doesn't need it. It has a stripped down version of DirectX 9 with all of the backwards compatibility and bug checking removed.
While it wouldn't improve the graphics it would likely make the client run a little better and remove certain graphics glitches that were introduced with Windows Vista and later (Vista etc. use a wrapper to support old versions of D3D)