For me the game just oozes atmosphere, even in the editor where it's just you on the map walking around.
The weather effects are fantastic too, one thing i would like to see added is a few little sound effects in regards to weather though, E.g when you change to first person view, i'd like the sound of the rain and wind to be far more noticeable.
The pitter patter of rain drops hitting your helmet, the wind howling and trees creaking as you walk through a wooded area, there's no greater depressing noise than rain hitting your helmet while you crawl into Op/sentry position or lay motionless in a field.
small details that i feel would have a huge effect in adding to the realism.
I agree. I am still in awe of that first mission in Hidden & Dangerous where you're in the rain, going across the railway bridge...
