I got this game today ^^ here is some info for you guys
Average completion time for a campaign on easy 1 hour (first time playing)
Special zombie kills 50
Normal infectes 2,300 (devided on 4 players)
When you complete a campaign a credits like stats will roll over screen ending it with "xxxx zombies where hurt making this movie" haha
xxxx being your total kils for this "run"
Witches and tanks are annoying:P
I just played a little today and got 2000 kills, i guess you can get over 5-10000 kills a day :O meaning that 53,595 kills achievement is easier than i thought and xbox splitscreen co op ftw.
All hail zombie genocide maniacs like us :D