Based on AMD's reference design, the cooler is up to the task of keeping temperatures reasonably low.
Compared to the stock Radeon HD 7970, power consumption goes up slightly with the Double Black Diamond. In general, the 7970 uses noticeably more power than its main competitor, the GeForce GTX 680, and also the top end video cards of last generation.
Ending this section with noise, I don't yet have a standardized practice in place studying the noise output of hardware. But after using the Radeon HD 7970 while gaming, I do have some subjective observations. When idle, the cooler is essentially silent. With the load of an intensive game, things change on the noise front and the fan speeds up.
The cooler on Diamond's reference design based Radeon HD 7970 is capable of keeping temperatures low, but this also results in the blower needing to ramp up to higher speeds. When playing games, this results in a moderate hum. It's not quite at an annoying level of noise, but it's definitely noticeable.
The stock clock speeds on the Radeon HD 7970 reference card are 925MHz and 1375MHz (5500MHz GDDR5 effective) for the core and memory, respectively. Diamond's Double Black Diamond comes overclocked from the factory with clocks of 1025MHz and 1450MHz (5900MHz GDDR5 effective). This puts the Double Black Diamond in the same clock speed range as the newly announced 7970 GHz Edition which are 1000MHz and 1500MHz (6000MHz GDDR5 effective) for the core and memory, respectively. Through personal experience and based on the speeds of the 7970 GHz edition (essentially a speed binned 7970), I still expected the Double Black Diamond to be able to clock even higher. For our overclocking testing, PowerTune limits were boosted by 20% to raise the overclocking limit.
In our numerous overclocking attempts, I was able to eventually settle with a GPU clock speed of 1125MHz and memory clock speed of 1500MHz (6000MHz GDDR5 effective). This represents a gain of 9.8% and 3.5% on the Double Black Diamond's stock GPU and memory clocks, respectively. This is pretty good for the GPU clocks considering the Double Black Diamond edition of the 7970 doesn't have any special cooling, just the reference cooler. I expected a more from the memory though, as 1500MHz is within the spec of the Hynix modules used. In any case, the GPU clock speeds of the Double Black Diamond are well beyond the 7970 GHz edition, with memory clocks matching.
For Metro with maxed out settings at 1920x1080 resolution, this results in a performance increase of about 6% over the Double Black Diamond's stock clock speeds. Compared to the reference design Radeon HD 7970, our manually overclocked Double Black Diamond is 11% faster.