ATi pushed it with the start of the X1800 series, and ATi does it better. Actually, ATi cards are currently being used by a guy named Mike Houston and his team at Stanford.
You can read up on him and his projects
here.
Also, if you visit and do searching of his posts at the Beyond3D forum you'll find him talking a lot about the GPGPU (the first GP stands for general purpose) performance the X1K series from ATi compared to Nvidia 7 series.
Also, realize that the 7900 is just a clock improved version of the 7800, other than that there's no difference expect for transistor savings, which is always standard.