well obviously THAT'S done in Adobe After Effects, hurr hurr says it in the title. but the original video you posted doesn't have any slow-mo/smoothness effects, that's how final kill replays are in MW2.
edit for more clarity i hope: the original video had no editing that effected FPS or smoothness or whatever you're saying. it looked like he did do a few stupid effects in a few places, but the slow-mo is just how final kill replays are all the time for everyone.
