The ASUS ROG ARES II is the pinnacle of this generation of graphics cards. It is based on two AMD "Tahiti" GPUs that are, each, overclocked out of the box - to clock speeds beyond those of the HD 7970 GHz Edition. Thanks to an on-board Gen3 PCI-Express bridge, it also maximizes available bus bandwidth.
In games where CrossFire is working properly, we see amazing scaling that often reaches twice the performance of the HD 7970 GHz Edition. We see the ARES II beat the GTX 690 by around 15-20% in these games. However, scaling does not work all the time. Six out of our nineteen titles show lower performance than expected: Assassin's Creed 3, Batman Arkham City, F1 2012, StarCraft II, Skyrim, and World of Warcraft. These are not insignificant games but AAA titles. Especially Far Cry 3 and Assassin's Creed were basically unplayable due to the massive stuttering that we experienced. Our gaming experience with CrossFire turned off actually ended up being smoother. Generally, AMD seems to be lagging behind in driver support for the latest games. You often have to wait for proper driver support when a game has been released, while your NVIDIA friends are, in the meantime, gaming happily. We, of course, can't blame ASUS for this, but such shortcomings have to be considered when looking at the ARES II.

Cooling performance is excellent due to the integrated watercooling solution that seems rock-solid and is maintenance free. Even heavy overclocking temperatures stayed in perfectly safe ranges, something that wouldn't have been possible with an air cooler. The added fan on the card helps keep secondary components, like memory chips and voltage regulators, cool, but I would have, instead, preferred a full-coverage waterblock to keep these components cool. ASUS decided to use a unibody cooler that is milled from a single block of metal. This greatly improves the product's feel, giving it a sense of the high-end, similar to what NVIDIA did with the GTX 690.
Idle fan noise is a bit high, and a low-noise experience would have been no problem with better fan settings. Fan noise is, under load, pretty quiet given the performance class of this card - it ends up being significantly quieter than the GTX 690. ASUS also included a second 120 mm fan with the ARES II, which is a nice addition if you want to tinker around with the card. In our testing, it dropped temperatures by 3°C at the cost of increased fan noise. When I installed both fans, I noticed an oscillating hum coming from the fans once they ran at higher RPM. This seems to be an interference problem based on the fan's rotational speeds not being 100% identical.

Power consumption of the card is shocking. We measured 650 Watt in Furmark and 375 W during typical gaming. I strongly recommend pairing this graphics card up with a decent power supply of at least 850 W or, better yet, 1000 W. Power consumption in non-gaming states is high as well, and using the PC several hours a day for things other than gaming might have an impact on your monthly electricity bill.
Overclocking worked very well, better than expected. It seems as though the GPUs for the ARES II are manually sorted for maximum overclocking potential, which shows in our overclocking results. We see clock speeds higher than 1200 MHz, which is typically only reached on single-card setups - the low temperatures provided by the cooler probably help a lot as well.

As expected, pricing of the ASUS ARES II is very high with $1599. The included suitcase, goodies, and its limited edition status cannot mask that. Considering that the GTX 690 is available for $1000, which scales well too, and scales in more games, I find it hard to recommend the ARES II over the GTX 690 for the pure gamer. If you are an overclocker on the hunt for benchmark scores, you won't worry about CrossFire profiles for games, and the option to adjust the voltage will be much more important to you. Remember, the GTX 690 supports no real voltage control.