Multi Monitors are nothing new, but actually in a properly usable format like that they are currently exceedingly limited, you basically have the option of Matrox TripleHead2Go (which is ~£150, and only supports 3x 1680x1050) or SoftTH which is software that requires tweaking and also has a substantial performance hit over the hardware version.
Eyefinity gives the flexibility of SoftTH but with no performance drop, and that is a big chunk better than anything else available.
I think you'll also find that the majority of sim gamers (Racing and Flight especially) either would love to have multi-monitor, and in the case of quite a few already run it with either of the two options above, and are looking forward to doing it all within the graphics card.
It'll also benefit quite a few other games as well, although some (like FPS, and Racing sims for that matter) wouldn't really suit a 3x2 setup like they show, but 3x1 or even 5x1 would be awesome...
Of course 3x3 would be best for an FPS