Sorry, didn't realise someone had responded to my post way back...
Eyefinity is just the name AMD gave to the ability to use one or more 5000 or 6000 series Radeon graphics cards to play across multiple monitors (up to 6 or so, if you have the right card or cards, I believe). The corresponding Nvidia feature is... Surround, I think? Or 3D Surround maybe. Anyway, with that one, you always need at least two graphics cards, in SLI mode probably. That would be the major, or maybe only, diffference.
The setup I'll have is 3 Full HD IPS (better off-angle viewing, basically) monitors side by side, to create a panoramic kind of view. I think the FoV (field of view, for example in Oblivion.ini) setting will be modified for this, suffice it to say.
With these monitors, I could also try, say, 3240x1920 instead (three in portrait mode, side by side).
Thin bezels are nice for these purposes, btw, in case anyone's considering it. :yes: