I'm too busy writing a final paper to play, but I ran through the demo stage once on single player and it was great (although the AI of my teammates left something to be desired).
Even playing with random people on Xbox Live, it's been really fun.
So far, everyone has been pretty good at it, and I haven't had to deal with any chucklefucks who try to ruin the experience for everyone else, which plagues virtually every other game on Live. Given the fact that Live is mostly populated by individuals who can only be classified as subhuman, this is saying something.
Call of Duty 4 has probably caused me to mute at least half of the Xbox Live user base.
PC people are usually snobs, but since its only been out for a few hours everyones been pretty nice. I expect this to change a month or so into its release.
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"Moris should be here soon to rub it in my face..." -Pizza