Overclockers Online has posted a new review on the Sapphire HD 4850 X2

One of my biggest issues with high performance is the high levels of heat generated and that often means loud cooling. I'm completely surprised by how well the HD 4850 X2 cools itself, I was skeptical that the two tiny heatsinks would be able to do the trick, especially when there's probably more metal on the shroud than with the heatsink. However, with the latest BIOS flashed onto the card, Sapphire has managed to balance performance, heat and cooling noise. I was still able to achieve a modest overclock while staying at reasonable temperatures and quiet cooling.

Sapphire HD 4850 X2 Review