What I want to know is why is eyefinity designed only for a flat array of displays?
In MSFT flight sim, you can open a window and specify a view for that window. You can then put that window anywhere in your display area. So what if you could create a view representing looking left 45 degrees, and another representing looking right 45 degrees. Then you could angle the peripheral displays towards the user (at the intended viewing angle) and get two benefits: 1) avoid the visual distortion that would be caused by placing a forward-facing image at an angle, and 2) increase the overall horizontal viewing angle. THAT, in my opinion, would be something. And yes, you would have to turn your head, but that's the point. In a real race / flight / war / fight / whatever, you have to turn your head.
I would take such technology, and use three projectors to have front, left and right wall images. THAT would be immersive.
I too believe that eyefinity should allow for mixed monitors, in terms of resolution, orientation and pixel pitch. The center monitor should have a higher resolution (e.g. 1080p or 2160p) since that's where the eye can see best. The side monitors really only need something like half of that to still provide an immersive experience.