The Windforce line of video cards is can be good but you need a case with very good air flow. The way the cooler is designed in a way that makes the heat flow into the case instead of out the back of your case.
If you go for SLI, you must make sure you have plenty of room between the cards the cards will overheat in no time. Trust me, I made that mistake with a pair of 580 (3GB) Windforce and had to change motherboards to get enough room between the cards.
Despite that and a modified Cosmos S case ( 2X high CFM 120mm fans blowing onto the cards) plus 3 top exaust fans etc.. I cant OC the 580 above 800Mhz. Technically these cards should hit at least 850Mhz.
That being said, these babies dont make much noise and do run very very cool in the right case!