The Nvidia GeForce GTX 550 Ti that this new AMD offering was supposed to blow out of the water actually stands up for itself very well. It's pretty much a dead heat between the two in both versions of DirectX.
Aand as they vie for the lead in single frames, the Nvidia GeForce GTX 460 trounces them both.
DirectX 11 tessellation performance
DirectX 11 gaming performance
DirectX 10 gaming performance