I have several machines with multiple monitors: two desktops and a laptop with a dock. They each have a different graphics card: Nvidia, ATI, and Intel. Each one supports multiple monitors flawlessly without having to do that annoying twinview thing anymore. Docking and undocking with the laptop automatically adds or removes the second screen; I even configured Gnome 3 to move the applications bar to the larger secondary monitor when I'm docked and back to the laptop when I'm not. On one machine I have the secondary screen have an independent workspace and another I have it change with the workspace: I'm still trying to work out which I like better.
So in summary, my experience is just the opposite of what you claim: multiple monitor support, on different chips, out of the box with no configuration.