7950GX2 Dual Monitor

Just thought id let every one know that the 7950gx2's will run two monitors but you will loose half the power of the card. As you have to turn off SLI.
Can any one even favom a reason for this?
As I understand it SLI is built on Old voodoo technology but updated for todays GFX cards.
Y isnt this problem mentoned on the box or on any of the websites advertising this problem?
I find this very demorolising and am begining to question whether I should have stuck with Nvidia or move to ATI like so many others.
Any comments on this would be nice.