Nvidia cards run hot. I have a 5850 taking 110 seconds for a a WU and its at 68° even after days or crunching (while beeing in the same pc as a Q6600 overclocked to 3ghz). But then with a card that can do cuda you have a lot more options on crunching. But if you are concerned with heat and power consumption ATI/AMD seems to be the better choice.

It gets noisy but crank your fan speed up, that will help a lot on the cooling. I find that the auto function, even when you tweak it's thresholds is not very good at all. I run mine in manual, and don't mind the noise so have it about as high as it will go. It keeps the card in the mid 50's

Aaron