rFactor's support is just as good (single-screen GUI, centered HUD, 6DOF head positioning), although some mods unfortunately do not model the entire car interior. That's what you get with an open-architecture sim, though.
rFactor wasn't always this good, but recent patches have added a lot of game features that include improved triplehead support. rFactor is also the only game that I know of that has an option for displaying the three monitor's views using independent fields of view, allowing you to see more, and see it with less distortion.
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Kudos to racing sim devlopers who get it right. 8)