Yes, I had this happen in one of the "white mansions with the piano."

I was upstairs, my buddy downstairs swinging an axe to hit a zombie, and ended up hitting me!

I had this dirt issue while proning by the construction site in Berezino. I was actually trying to see across the incline, not up or down it.

Ditto to all the above. Outside cities 60-80FPS, inside cities there is a drop. Inside big cities like Cherno, Zelenogorsk, Berezino have massive drops in to the high 20's and low 30's depending if I'm looking towards a lot of buildings and buildings behind buildings.

i5 2500K @ 4GHz
8 GB DDR3
GTX 680 superclocked 2GB
Win 7 64bit