I have used the DBA rotors on 4 different race cars over recent years of which 3 of the cars I actually raced myself.
They braked as good as the standard rotors but actually lasted longer, in fact the disc life was twice as long in all cases than the OEM rotor.
This was race conditions only not road use with a variety of pads also.
On my old R32 GTR I did a back to back temperature test at Eastern Creek (also using an infrared temp gun) and found that the Kangaroo Paws actually ran about 10% cooler than the OEM disc.
This was my experience.
Ive had nothing but good results with DBA rotors.