After reading a lot of reviews, game wise at 2560 res, the 6990 is in the lead by around 10%. Including older games where both cards get 100+ fps is where the 590 closes the gap to around 5%. IMO, the 6990 is a clear winner in games that matter which is able to stress these cards. This isn't surprising since we knew the core clocks. The 590 is essentially a gtx570 SLI. You can also cherry pick to make the 570 SLI appear even with the 6990, but we all know its not.
Given the target market towards enthusiasts, as others have mentioned, only a few factors influence buyers:
1. 2560 res and multi screen performance.
2. Overclocking potential
Noise matter but not as critical. People spending that much on a rig will have water cooling setups as these cards vent a lot of heat into the case, limiting the overclock on other hardware.
Edit: as for the dead cards, i'm going to give NV benefit of doubt and assume they just messed up shipping drivers without proper protection. If this continues to happen with the new driver then its a huge problem, otherwise its not a factor.
Edit 2: The short PCB and lower acoustics definitely has a big drawback:
http://www.hardware.fr/articles/825-4/dossier-nvidia-repond-amd-avec-geforce-gtx-590.html
http://www.hardware.fr/articles/747-22/maj-dossier-cartes-graphiques-degagement-thermique.html
compare the surrounding temps as well as the pcb temps, at 112C its going to cause a lot of component stress. This card definitely needs water cooling, period.