hmm I guess that explains why it was never mentioned before. I suppose it really only becomes feasible with a third monitor for the middle.
If you only play FPS games then you are correct.
If you play strategy games, it's fine. I remember using my dual 17" monitors on my 7800GT in span mode and playing games like Rome Total War across dual monitors, 2560x1024.
At one point I did raise the issue in some comments to an AT article, only to be told by the author of the article that what I was asking them to do (test running across dual monitors) wasn't possible.
It was. I knew it was because I was doing it!
All Eyefinity adds is a third monitor to the equation, which makes the whole setup more broadly gaming friendly for those where action is focused in the middle of the screen (such as FPS games).
Having said that, we're already had hardware (TripleHead2Go) and software (SoftTH) solutions which have allowed triple monitor gaming (on non-matching displays even... I used SoftTH with a 7800GT + 7200GS spanned across a 17, 20 and second 17" monitor).
Eyefinity just tries to make the whole system more consumer friendly, and offers more options (vs Triplehead2Go which is severely resolution limited and horribly expensive) and without hacks (like SoftTH uses).