Power-draw and temperatures
R5870 Lightning uses the same core voltage as the regular HD 5870, but the use of a higher core speed and multifarious extra components on the PCB push power-draw some 40W higher.
Temperatures
Catering for the extra 40W, the Twin FrozrII cooler is able to beat out the basic card's under-load temperature. However, as a comparison, the Sapphire HD 5870 Vapor-X (870MHz/5,200MHz clocks) draws a system-wide 316W and the cooler is able to keep the GPU to 64°C - 12°C 'better' than the Lightning and quieter to boot.
