Nvidia Surround may seem like a half-arsed rush job, but the technology is basically already there - it's not like they're doing it from scratch. Or at least if they are then I'd be VERY VERY surprised, and it would invalidate a lot of my arguments :-
I don't think that Nvidia surround would ever have been made if ATI didn't make Eyefinity. Fermi was originally intended to be released around the launch of Windows 7. The hardware were delayed, but if Nvidia had intended to release surround with it, they probably wouldn't have delayed the release 8 months after the launch of W7. Though Fermi was delayed, Nvidia surround will also support GTX260 to GTX295, so they had hardware to develop the software on.
The tech is not basically there. I also think that Nvidia will use some sort of SLI Mosaic, but remember that the requirements in games vs. applications are a bit different (look at Eyefinity vs. extended, where you have PLP support in extended, but only in windowed can you use PLP with Eyefinity).
Nvidia surround is depended on SLI. Hopefully they will implement a fallback option where you can use a single card for rendering and second card for output like softTH. Otherwise, all issues related to SLI would potentially be a larger issue in surround.
Using dual cards (regardless of ATI or Nvidia), have a potential of creating latency, sync and bandwidth issues.
Nvidia is facing the issue that they also would need to sync 3 screens over PCI-E and SLI bridge, while ATI are syncing them on the same card. Each frame needs to be perfectly synced (unless they want an uproar from gamers complaining about everything from screen lag to tearing) and latency, sync and bandwidth issues that already exist in SLI can break the sync over 3 screens.
If the "wait for sync" will be too long, gamers would complain about input lag and how surround kills their headshots. Gamers like to complain and keep the vendors in check. :lol:
As we know from SLI and Crossfire, there is no "one solution fits all games", so if surround becomes to dependent on SLI support, the experience might differ from game to game on SLI support alone. Using Mosic also might prevent the use of AFR or split-screen(scissor) rendering, so it might require a separate SLI profile.
I am painting this a bit black, but its to get some perspective here. Many of these issues aren't solved over SLI already, so it might not be realistic to believe that they will be solved when you add 2 more screens and 3D support.
I think we all (regardless of hardware) hope that Nvidia will come with a perfect solution that will raise the bar for multi-mon support, but we don't know anything before we actually have seen it in action. Nvidia IS facing hardware issues that needs to be solved and some that might not be possible to solve with current hardware. The important thing IMO is that they are coming with a solution and the competition this will bring, would force some developing money into improving on it. :)
One thing I personally hate, is if I would be locked to one vendor due to feature support and without Nvidia surround, I would be once I get my own setup (wife factor, so I only get one shot of making one, so this one must count). :P