I've had an eyefinty setup for almost a couple of years now with a 6950 and the default support for most A+++ titles is pretty good unless its clearly a console developer which has ported the title, for instance 2k games, in which case there can be problems. I'm at 5760x1080. It was more of a productivity effort for me at the time and I tossed up between a single 27" or 30" dell or the tri- IPS 1080p dells I eventually got. Screen real estate was what I was after and I was used to working with dual screens so three seemed the logical step up and its what I went with.
Recently I got another mini dp to dp cable and connected another of the dells through dp so I could use the HDMI port at the same time as one of the DVIs on the card shares its port with the HDMI so you can't use them at the same time. Moving the third monitor to the second mini dp solved this so now my monitors can display at the same time as my PJ which is nice.
For the most part newer games will offer some support naively but as you say they will often do this by narrowing the FOV rather than extending it. As an example NBA 2k12 is guilty of cropping into the 16x9 native frame so heads and feet are cut off, making the game near unplayable in eyefinity. There are some tweaks but none are satisfactory (that I've found) mostly its a let down. Some just don't work right (Gratuitous Space battles I'm looking at you!) but theres nothing preventing you from just playing in 1920X1080 mode on the central screen.
When the title has full support (say BF3) its very good. The HUD and the FOV are re-sized to make sense on the full span of the monitors and its as simple as changing it in options if you want to go to a non-native display size ( say 4800X900) for performance or what have you. Totally seamless, flits between them without issue and re-sizes when you return to the desktop.
Updates seem to fix issues with eyefinty such as misplaced HUD or funky menus spanning across screens but you have to wait for an update so you're in the hands of the developer but this has improved in the last year. As an example as to why the HUD position can be an issue I've had difficulty getting into CIV 5 because the HUD sits left and right on the screen and this can make interacting with the game a bit of a chore as you're constantly moving from extreme left to extreme right during the course of a turn. It really depends on the game and its a mixed bag. A+++ titles are usually pretty good at supporting it but YMMV. Dirt games run very very well even on my card and really look good.
As far as the desktop goes there are a number of different ways for the span to behave once its all plugged in and its pretty much what you would expect with a few downsides. In CCC you must first setup the display span in the eyefinity section turning the three monitors into what will be registered as a triple width single display. Using the Hydra grid tool you can then set window behaviors so the three monitors can behave independently as single displays without the entire width span but this can be a bit buggy and not all my software supports it. As in they behave oddly like they dont resize themselves to the single display and continue to render themselves at 5760X1080 with a horizontal scroll or worse with nothing at all. Again its only an issue some of the time and is usually resolved by full spanning the window but its something to watch out for.
You can also get the three monitors to behave independently (As in not a span) but the trick here is that if you want then to play a game in eyefinity you will have to change the desktop back to your eyefinity span before you launch the game. It wont automatically engage eyefinty. This is frustrating.
Finally, the biggest frustration is that CCC can be a bit buggy. I have hotkeys setup to engage and disengage the eyefinity setup as I don't use all my software (or it doesn't work) in eyefinity. But flicking between eyefinity and normal mode will often crash CCC requiring a restart. Even when it does work it can leave your start menu bar (which I keep attached far right) and your desktop icons strewn everywhere or other wee bugs which popup almost always requiring a restart. This can be pretty lame. Otherwise when it works it works pretty fluidly. Gold star for Just Cause 2 which plays great on my card, looks fantastic and has worked since day 1 (more games on that engine please?).
I dig it to be honest, if you're used to dual displays it can be much the same if you want. And hell IPS monitors are so cheap now, well...
I haven't tried the NVIDIA surround or whatever, I imagine its the same mixed bag but who knows. Its taken ATI quite a while to roll out some of these fixes and support tweaks so NVIDIA may be behind in developing that stuff but I don't know. Obviously this can use all the GPU horsepower you can throw at it in a modern game.