From what I've experienced, it seems BF is a bit older crowd. But with all of this media attention for bf3, I'm pretty sure there will be a lot of curious youngsters from COD.
I think they will be disappointed since bf does not measure kill streaks and your kill count doesn't show to other players. No more bragging rights. Most of the points you get is from teamwork.
I use to play COD, but BF has always been a better experience for me. Both games are not similar in anyway and provide a different experience that each title has mastered. COD run and gun'em. BF a bit slower paced, by pushing enemy forces back to get to an objective, but BF has a lot more variables that can change the tide of a battle (tanks, jeeps, planes, helicopters, etc...).
1 more hour before I pick up my copy.