As was mentioned last week, the "vga_switcheroo" that allows for dual GPU switching / hybrid graphics support on some notebook computers is now being pushed into the mainline kernel. This support isn't as polished as what can be found on Windows Vista/7 with real-time switching, but for now on Linux the X.Org Server needs to be restarted when switching between the graphics processors. The NVIDIA switching support is also still immature compared to the ATI and Intel support levels.
Beyond the Linux dual GPU switching support, the Linux 2.6.34 kernel DRM also features the initial ATI Evergreen/R800 "Radeon HD 5000 series" kernel mode-setting support, initial power management support, hardware I2C engine support, the R600 command stream checker, and other changes. The initial open-source Evergreen support does not yet offer any 2D EXA/X-Video acceleration but just basic KMS support.
The Nouveau driver contains an interface break that will require updated libdrm and DDX driver code. This is permitted in the mainline kernel as the Nouveau driver has not yet left the staging area of the kernel.
On the Intel side of this Linux 2.6.34 kernel DRM code there is initial Sandy Bridge support well ahead of the product's availability.
The first (of likely a few) DRM pull requests for the Linux 2.6.34 kernel can be read on the mailing list.
As always, we are benchmarking the very latest Linux kernel code on a daily basis over at kernel-tracker.phoromatic.com.