We finally killed Illidan tonight, after working on him for 3 weeks. Which means we have actually "beaten" the game, so to speak... or at least until the next content patch comes out. The fight is an absolute blast. Twenty minutes, 5 phases (the last of which is ridiculously epic), and oh so many ways for things to go awry. It's fights like Illidan and Prince and Archimonde that keep you hooked on progressing in this game, tough often to the point of pure madness, but the satisfaction you get when you finally beat them is awesome.