3 screens for gaming

I have a 3x1200p eyefinity setup and when it all works, it's pretty awesome. A few things to bear in mind though:

a) make sure you have the graphics horsepower to drive 3 screens. It's trying to render 3 times the pixels so has a massive hit on performance.

b) lots of games don't work, or work with significant flaws (for example, apparently Eyefinity renders XCOM just fine, except that everything's upside down).
Check the games you want to play on WSGF: http://www.wsgf.org/mgl
Your best bet is just to find the link to the forum thread and have a read of what people are saying, you usually get a pretty good indication of how painful it will be. Pay particular attention to AMD Eyefinity or Nvidia Surround (depending on whether you have an Nvidia or AMD card), some games will work with one and not the other. The site is also pretty good at providing info on hacks/work arounds to get games to work that otherwise don't. I can be a frustrating/messy world. Like I said though... when it all works it is a thing of beauty!

c) even when it all works, I don't think MOBAs are the best use-case for eyefinity/surround gaming. 3xLandscape is just weird, great for flights sims and 1st/3rd person view, but not that helpful for top-down view, particularly when threats are just as often above/below you as they are to the left or right. 3xPortrait would be okay but you need screens that can rotate, or a specialised stand with compatible screens (most are VESA complaint, but you'd need to check). Then you'd also be stuck with 3xLandscape screens at desktop, which isn't ideal, unless you could find screens or stands that rotate easily.
Even if you can have 3xLandscape, you get a massive screen but screen scrolling becomes an issue. I play LOL and don't bother with eyefinity. Partly because it's pretty screwed up for eyefinity (though I hear Nvidia surround works better for LOL), but mostly because the scrolling behaviour messes with my head, you have to drag the mouse so much further to move the screen. If you're quick with the centre view button, or stick with it long enough to get used to it, it might be fine, but I just found it frustrating.

If you have the graphics horsepower, are looking at games that have good 3-screen support and where the extra screen area is a benefit, then by all means go for it. But best to know what you're getting yourself in for.