Lankhorst covered the DMA-BUF, X.Org Server, DDX drivers, and RandR component changes being done by him, David Airlie, and others for supporting this multi/hybrid GPU technology that has been notorious under Linux. Maarten is currently employed by Canonical and they are hoping to have some early support in place for Ubuntu 12.10.
As covered in previous Phoronix articles, most of the mainline support is now in place with X.Org Server 1.13, the mainline Radeon / Nouveau / Intel DDX drivers, etc. However, more polished support should come in X.Org Server 1.14 for seamlessly switching between GPUs. Maarten is also still working on synchronization / fence support.
A demo of the primitive DRM PRIME / Optimus support was attempted from an Intel/NVIDIA laptop by Maarten, but it ended up crashing.
NVIDIA's Andy Ritger is at XDC2012 but he refrained from commenting during the session on the Optimus support in the proprietary NVIDIA driver that they have been quietly working on.