I think the people saying it looks like a cartoon are exaggerating. It doesn't mean it can't be dark just because of colors. I also think it's quite ballzie of Blizzard to add this much color - mastering colors in stuff like Diablo 3 is probably one of the hardest challenges for a videogame art director. And I gotta say I think it looks great, and it's still a dark feeling over it, despite the colors. So good job there Blizzard!
Now, give me a freaking betakey before I break something and go irl Diablo on Gothenburg city!!!!!!!!