My mate just bought this game and we played trough 80% together.
I 100% agree with what you said
As we were bouth high it was fucking scary first half of the game

After that guy with the freacky mouth and eyes died in what I must say was the most pitiful "boss" fight in history (he was just a normal enemy:S).
All the shit you said about the gun fights was 100% true, mostly ebcause we were figting normal people.. and the atmosphere just whent to a straight foreward shooter:S
Havent seen the last few lvls though, so cant comment on that.
Enjoyed the game but got mediocre after the halfway mark ike you said.
Keep up the good work