There isn't much to say about the new video card from Sapphire, since it isn't actually different from AMD's regular Radeon HD 7870 GHz model, not counting the cooler.
This might just be a tactic meant to make up for the fact that some HD 7870 GHz edition cards tend to sometimes crash and give a black screen of doom.
The cause is related to poor-quality capacitors, but the phenomenon happens randomly.
The new Radeon HD 7870 GHz with Dual-X cooling should be free of that issue and will ship soon, for $230 / 230 Euro.
The GPU operates at 1 GHz and the 2 GB of GDDR5 VRAM at 4.8 GHz, over a 256-bit interface. The necessary energy comes from two 6-pin PCI Express plugs, while monitors can link to the card via HDMI, DisplayPort and one of two DVI ports.