We always measure the temperature of a graphics card after two benchmarking rounds of Metro 2033. Normally we also use a temperature sensor to measure the temperature, but the design of the back of the card made that impossible in the case of the Ares II. We therefore only have the temperature as indicated by the drivers.
The watercooling works great. The Ares II registered 50 degrees, which is very good considering you have two overclocked GPUs. It's actually lower than many single-GPU cards. It also leaves enough overclocking potential, which you will see in bit.