Lag, Matchmaking, Killcams, Melee, Hit detection, etc..?
Just a few of the rather MAJOR things you should probably consider fixing before trying to charge people for extra content.
I loved the demo, yeah it still had the issues but I loved the potential the game had. Having bought it and played in on/off since release the updates have been woefully inadequate at solving the problems with this game. I'm hearing that Brink is another example of a game with so much potential and new mechanics RUINED by major bugs in core features.
Stop polishing your games after release, make the game complete BEFORE release. And if you can't manage that don't start expecting people to pay for crap DLC...