KitGuru investigates how serious the problems of NVIDIA's dual-GPU GeForce GTX 590 card are, you can read their piece over here.
Testing the temperatures of a video card is a difficult task, many publications use simple driver readings, and others can use diodes which can be attached to various positions of the PCB and cooler. They are never totally accurate. It is worth bearing in mind that often software related thermal readings can also be wrong.
One KitGuru reader brought it to our attention that Hardware.fr use a thermograph to accurately measure video card temperatures. Their GTX590 testing showed a reading of almost 112°C under load.