I’ve complained often enough about how difficult Infinity Ward makes their Call of Duty games.  In Call of Duty 4: Modern Warfare, the veteran difficulty mode was flat out impossible.  No longer were you playing a game, you were trying to exploit any small game weakness to get past the gauntlet the game designers had laid out before you.  With Modern Warfare 2, Infinity Ward made some changes to make the gameplay feel a bit less like getting curb stomped but still be challenging.  Nick Werner from the Machinema series All Your History makes some great commentary here about the subtle changes to gameplay that Infinity Ward introduced in Modern Warfare 2.