As DLC comes and goes I think Firaxis has handled it quite well. I'm of the opinion that DLC works best in games with a high replay value, like Civ V. If I buy a new civilization, it affects my game every match that I either play that civ or it is played by one of the AIs. It feels like I get value for my money. I contrast, action adventure games(e.g. Mass Effect) I tend to play only once for that one grand experience. I don't want to return to them, play through the story that I've already seen to find that one extra mission crammed in in the middle of the story. For games like that, I don't feel like I get any value out of my money when I look at the DLC.