Like any consumer, I wish that all of the downloadable content was either free or already accessible on the disk when I buy the game. For example, I play Dead Rising and they have downloadable "keys" that lets you change into different outfits. These downloads are free.
I don't own 2k8 yet (getting today), but I already know going into it what is and is not included in the game. This helps me decide if the cost is worth the game. For example, I did not buy the game at $60, I waited until $30 because it wasn't worth it to me at $60. Now, I can say, if I want the game and the downloadable features, the game costs $35. Now, the question is do I feel like it is worth it to me.
Look at it another way, if some company tried to sell you Pong for the 360 without any update or anything -- still the 1970s version -- would you pay $60? No way. How about $5? Maybe, but still doubtful. However, if they said, okay, we are going to sell you the basic game for $5, but if you download some update that unlock things on the disk, you can also play Halo 3. The downloadble keys will cost you $50 on Microsoft Live. Now, all of a sudden, it might be worth it to you. Does that mean that they should have given you Halo 3 for $5 just because it was already on the disk? I don't think so.
Here's another example. I have basic cable (none of the premium channels). When I go to the HBO stations, it is blocked but I am told that for a little extra I can get that option. The feed is already coming to my house, all that needs be done is the cable company needs to flip a switch and I get it (much like having to download an unlock key). Does that mean that I should get it for free becuase it is already there? Of course not.
As a consumer, you want to get as much as you can for your money. As a seller, the distributers want to give you as little as possible for your money. The genius of capitalism is that a consumer and a seller meet somewhere in the middle, when the consumer gets enough for their money and the seller doesn't part with as much.
I guess the big question is, Paco, would you be willing to pay $65 instead of $60 for a new game with all of the keys unlocked? If not, then the cost/benefit analysis favors you not buying the game. If you do, then you buy it.