Single Heroic 26/9/07, Co-op Heroic 27/9/07. I am now in the process of gathering a semi decent team to tackle Legendary. All skulls found 3 days ago. Still a couple of Terminals to get yet though, or rather, go back to and actually sit through like you are supposed to.
I have finished the fight solo on Easy, Normal, and Heroic. I'm working on Legendary with my younger brother (he really wanted to play, and I think he was about ready to kill me in my sleep in order to do so).