Mike Schramm of Joystiq with the breakdown of killstreaks in Modern Warfare 3:
In place of the old Killstreaks system there’s a new setup called “Strike Packages,” organized into three choices: Assault, Support, or Specialist. The Assault Strike Package works basically the same as the old killstreaks did, where you rack kills up to earn in-battle bonuses, like UAVs and airstrikes, or new weapons like a remote-controlled helicopter or a ground-based attack drone.
I like what I have heard about the different types of packages you can have, especially the one that benefits team play. But based on all the information I have read I am still worried there are going to be some balance issues, which was the biggest problem with Modern Warfare 2.