I have noticed screen tearing also. I also noticed that sometimes when I am running, people just spawn in front of me instead of at a distance. But overall, an amazing game. I beat a couple of weeks ago. I got the PS3 version for PSP connectivity and the weapons you get are very useful in the beginning since they are much better than the beginning weapons.
Also, anyone notice how Lucy looks nothing like Kristen Bell. THQ did the same thing when they made Tera Patrick in the game and it came out looking nothing like her. Wish they took more time with that.