you end up with almost 2x performance for 50% more money.
That is simply not true at this point in time..
Actually mm said it best, (abit extreme may I add:
You\'ll buy a 2nd card for 10% performance
SLI has yet to prove itself as a doubling performance solution. Sure in certain situations SLi can achieve 70-80%. For the most part SLi economically is a waist of Money, and is really only benificial for the uber geek who wants to run his game at insane resolutions with AF/AA.
IF next gen ATI Crossfire or SLI can offer an 80% perofrmance increase without having the limitation of only being able to acheive this in certain settings, but rather as an overall performer, then and only then would I consider making the leap into purchasing a setup.
I reckon the Advantage to Multi Gpu setups is so that instead of throwing away your previous gen card, you can continue to utilize your invensment by enhancing it\'s performance for half the price of what it would cost for a new State of the Art gen Card.