The Linux GPU switching (a.k.a. "Hybrid Graphics") still isn't as clean of a solution as what can be found with the Windows 7 support where GPUs can be switched between in real-time, but that's because of limitations with the current X.Org Server. However, with the Linux 2.6.33 kernel having just been released, David is hoping to finish off this work that he calls "vga_switcheroo" and to push it into the mainline Linux kernel.
The vga_switcheroo kernel code is now up to its 13th revision with some of the later changes being ATRM support for the Radeon BIOS, a fix for resuming the Intel GPU, and avoid putting an already inactive GPU through suspend-and-resume. David Airlie talked about the revival of this work on his blog. This Red Hat engineer has also started pushing patches on the DRI development list as well as the Linux kernel mailing list.
Assuming some of the remaining issues are cleared up in this code, GPU switching in the form of vga_switcheroo should be here with the Linux 2.6.34 kernel release.