It depends what kind of DLC it is. For example: I'm not gonna buy the extra costumes in Street Fighter IV; the game experience doesn't change. It's the same fucked up thing as secondlife and other internet based games where you have to pay for everything; clothes, furniture.... WTF? I'm not going to pay cash for in game clothes.
Maybe map packs are nice for people who really like their shooter. Most of the time I play a shooter for a couple of months and then I'm gonna buy another game which is a totally new experience, but I can see the reason that people who play hundreds of hours COD or Halo wan't a change in scenery.
And then there are the DLC I do like: complete new chapters of a game like Fallout 3 and GTA IV. Those are imho really an add-on, the same as 10 years ago before the DLC even was born.







