OMG! This game ROCKS! All I gotta say is just buy the game. SP is really interesting despite what reviewers are saying. But the MP is worth the $50. It's fast paced deathmatch and with the Create-a-Class, it's always fun to mix and matchs perks.
For those who are getting it today or later, you have to rank up in order to unlock new classes and Create-a-Class. I'm already up to Lance Corporal II. Perks are sweet!
Also, the first level is INTENSE. Activision and IW did an excellent job on this game.
EDIT - If you want it today, go to EB or Gamestop. Walmart won't have it until tomorrow! Trust me, I've been all over town for it.