Since last December there's been a Sandy/Ivy Bridge Gallium3D driver developed by Chia-I Wu. The work mostly comes as an experiment or toy, but last month it was merged to mainline Mesa.
While this driver, which was renamed to "ilo" from "i965g" or "i965g-next" to avoid confusion with Intel's official Mesa (classic) DRI Driver, it's still being developed with new commits almost daily.
For those not following Mesa Git on a daily basis, there's a stream of new activity since the driver's introduction last month. This work can be seen by searching for ilo. Among the advancements made in just the past week for this Intel Gallium3D driver include support for stencil resources on Ivy Bridge and later, support for hardware primitive restart, new pipe format support, support for mapping with a staging system buffer, and various clean-ups and code reworking/refactoring.
New benchmarks of this alternative Sandy/Ivy Bridge open-source Linux graphics driver will come when it's been developed further.
Separately, for those curious about the recent prospects of the older i915 Gallium3D driver possibly becoming the default over Intel's i915 classic driver for supporting up through i945 IGPs, there isn't any new information. Intel ended up bringing OpenGL 2.1 to classic i915 to compete with that older Gallium3D driver, so it seems they aren't quite ready to abandon their older code-base quite yet.