Try turning down anti-aliasing to save a bit of graphics memory and see if you notice a major difference in frame rates.
My experience with Eyefinity is that the experience tends to be better when sitting back slightly farther (similar to how you might do with a console and a TV but not quite that far back). AA should be somewhat less of an issue at this range so I'd try that first, though I'm sure a few games with poor alpha transparency may still look a little jagged at times.
Battlefield 3 is another matter. I'm at a mixture of low and medium detail and it doesn't feel smooth enough? The reported FPS hovers between 18-36, so there's noticable jitter and it has crashed on occasion. It never used to, but i've noticed it's pushing all 8 modules of the dozer to near 100% usage, but crucially not loading both GPU's 100%. It actually only uses 60-70% across both, so if logic is right - im being held back elsewhere?
It's been a few months since I've actively played BF3 but when I upgraded my rig last year, I made a few observations:
1. My brother's 6950x2 config was also a stutterfest even on medium/high settings
2. Three 6950's won't do the trick either - only a marginal (nearly imperceptable) improvement
3. A single 7950 isn't enough to run BF3 at 6408x1200 smoothly on Ultra but is okay-ish on medium/high
4. A single 7970 also isn't enough to run BF3 at 6408x1200 smoothly on Ultra but good on high
5. Two 7950's will almost run Ultra smoothly but better on high (70-80% scaling)
6. Two 7970's will run Ultra just fine (90-100% scaling)
Our conclusions were that XFire scaling on 79xx cards is far better than 69xx cards for BF3. Admittedly, I don't have any hard numbers any more but perhaps that helps.
2600K @ 4.8GHz; XSPC Rasa/RX240/RX120 Phobya Xtreme 200; Asus P8Z68-V Pro; 16GB Corsair Vengeance 1333 C9; 2x7970 OC w/ Razor 7970; Force GT 120GB; 3x F3 1TB; Corsair HX750; X-Fi Titanium; Corsair Obsidian 650D; Dell 2408WFP Rev. A01; 2x Dell U2412m