I actually have nVidia Optimus working pretty well on my Dell L501x with a Core i3 (Intel HD 3000 Graphics) and GeForce GT420M under Ubuntu 11.10 Oneirc with the nVidia blob drivers.

The two routes to this working is the 'Bumblebee' project which is where most of the initial work was done, contributed to by many people and then the original project owner declared as a mess. He then started a rewrite called 'Ironhide'. Read more on his blog. Anyway, seems like both Bumblebee and Ironhide seem to be in active development and mature enough to use. I am using Ironhide at the moment and it was easy enough to set up and does what it says on the tin. nVidia card disabled on boot, using the Intel HD graphics. Run an app with 'optirun <application>', and it enables the nVidia graphics for it, all works just fine, quit and it turns the card off again.

Actually quite painless.