Since February, the flow of patches for supporting Sandy Bridge using open-source drivers under Linux has continued. When it comes to the DRM/KMS Intel driver, there's been initial Sandy Bridge support since the Linux 2.6.34 kernel and has improved with each major kernel release since that point. We talked about the Sandy Bridge Linux work more extensively in this news post.
Most recently, Intel confirmed they plan to have their open-source 3D support readied in Mesa (via their classic driver, as they are currently not doing any Gallium3D work) this quarter, which will be in time for when the first Core i3/i5/i7 Sandy Bridge CPUs are available for purchase.
These very latest software components will not work their way into most stable Linux distributions by then, but can be easily built. For those shipping with a 2.6.34 kernel or later (such as Ubuntu 10.10), there will at least be some first-cut support available.
As the most recent advancement in Intel Sandy Bridge Linux support, Haihao Xiang from Intel China has published patches providing X-Video support for the next-generation Intel graphics core. These patches add around 1,000 lines of code to the xf86-video-intel driver in enabling this Xv support. Though a current limitation of this code is that shadow needs to be disabled (via the xorg.conf) for the X-Video adapter to work.
The start of the patch set can be found in this mailing list post on intel-gfx.
While it's nice to see X-Video support as another feature to arrive in Intel's Linux driver stack prior to this hardware even being released, it's H.264 VA-API support that we really want to see for Sandy Bridge in terms of better accelerating video playback on modern hardware. It was earlier this year when Intel delivered VA-API support for the Clarkdale/Arrandale hardware (current generation Core i3/i5 CPUs).
It's unknown though when we will see Video Acceleration API support for Sandy Bridge, as Intel also promised to deliver this video acceleration support for those running older GMA 4500HD-era hardware, but so far it has yet to arrive even though it was a Q3'2010 promise. It's upset some Intel customers.