A great performer in about three games.
And then you have the list of problems with the rest. Namely -
1. Game comes out and won't even launch. Have to disable Crossfire and wait for AMD to release a profile. Then you have to hope the profile actually works (as they never used to for me) before crawling the internet all night looking for the bodge. In my case it was usually to rename an exe file. That means you need to hack your game and hope there is a no dvd patch for it as otherwise you kill the registry entry.
2. A good 90% of games are not coded to understand more than one GPU. So, even though you may get it to like, work, it will be of no benefit at all (please see article above, 1% is about right).
3. Even when it does work you will still be subjected to micro stutter, post process flicker and delays with synchronisation of the GPUs themselves. All of which are visible and highly annoying. None of which happen with one GPU of course.
4. Your room turns into a Turkish bath and sweat begins to pour down your sides. The most I have managed on my Quad SLI rig was three hours of Fallout 3 and then I needed a bath.
5. The noise. Double the cards, double the power.
And so on.
No matter what AMD and Nvidia do you are still always going to be better off with one card. It won't change either, as I don't see people all rushing out to buy four cards. And it is a catch 22. Few people set up more than one GPU. A few of them decide to put their hands up and tell the truth and be honest - it's crap, and then put people off from wanting it (those with any sense). Thus, the market for multiple GPU setups will not grow, it will just remain within the "idiots circle".
When you are the minority it sucks. I know this, because I own a pair of cards that are less than two years from their manufacture date (mine are pretty much brand new) and they are already considered dead technology. I am talking of course about a pair of single PCB dual GPU GTX 295s. Cards that Nvidia made purely to wave willy and nothing more.
The drivers are consistently leaving them behind, and the shadow problems in Battlefield 3 have still not been addressed . Now at first I was hoping they would actually, you know? give a toss, and finally sort it out. But no. All I get are adverts for the 5 series.
Just think. Some poor sod (aka idiot) would have done £900 on those cards less than two years ago and be sitting here feeling really let down round about now.
The article I posted is absolutely spot on, and all of the time articles like those exist multi GPU set ups will not progress.
So get one if you want to wave your willy, but remember that you need to learn how to lie. If you care about actually gaming then you will be doing a lot less of it, so face that now before lashing out loads of money.