The first Service Pack for Windows 7 is going to be released soon and a Chinese website has gathered stats based on DirectX11 Performance of the upcoming pack. The cards used for testing were Geforce GTX 460/460 and the Radeon 6850/5750.
The first test was done using 3D Mark Vantage which is a Pure DirectX 10 based Benchmark. All the cards except the GTX 460 got a slower score than the Basic Version of Windows7. Coming to Direct X11, The games tested were (Heaven, Lost Planet 2, HAWX 2) which use a DirectX 11 Engine. Well the performance was better on the service pack but only a slight increase rather than a significant one. Only the gains made using the GTX 460 were seen clearly.
So it can be said that the new Service Pack will pump up a few frames in DirectX 11 based titles.