The DLC will do nothing but good for both gamers and Nintendo (assuming that Nintendo keeps their promise of only letting DLC being additional content, rather than content removed from the original that you then will need to pay for).
Gamers will get more replay value from their games and Nintendo will get more money. Only positive things in my opinion. Heck, if Super Mario 3D Land got some DLC levels I might actually consider replaying it for the first time in months. New levels for Mario Kart 7 would also be nice, but Nintendo seems pretty stubborn with this "only 16 new levels per entry"-policy, so I wouldn't bet in it.
As for your other points, I guess their validity depends on who you are asking. Personally, I don't care about any of them.







