ATI has been waiting a long time for this moment. nVidia has been dominating the top-end of the graphics card market for nearly two years now and, although ATI has come back strong with its competitively priced HD 4870 and HD 4850 products, there's nothing quite like being able to claim the top spot.
As you may have guessed from the 'X2' on the end, this card uses the same performance boosting method employed by the HD 3870 X2. Namely, taking two graphics chips, slapping them on the same card and using the wonders of Crossfire to make them work together to increase the card's overall performance. The big difference between this card and a standard dual card Crossfire/SLI solution is the fact that the X2 is platform independent so will work on any motherboard with a x16 PCI-Express slot, whether the chipset the motherboard uses is Intel, AMD, or nVidia.