Very good map, some unique mechanics, 3rd (or 4th, lost count) map needs a little work, try adding some guideposts or spraypainted signs around the complex, its easy to get lost, although fun and rewarding to explore. The whole "Catch up to the truck" bit sounded fun, but the long puzzling layout ahead kinda makes that hard to keep sense of. Also, the REQUIRED junp across that gap is a bit harsh, I got tanked and everyone done used thier first aid kits. If it wasn't for those healing stations I wouldn't have made it over that gap because I couldn't run. Alternatively, move a healing station to that room. It would also be useful to trigger a voice command "Over this" or something to that effect, as at first glance the other side of that clearing looks like a place for spawning megamobs, not meant for traversing.

Theres some bugs with the rain, "No matter how witty or funny a line is you're sick of it the 20th time you've heard it" Perhaps add a math_counter or something in there to limit the frequency the survivors can react to the rainstorms.
"Is it too cold for you crybabies"
It was meaningful once, but the 5th time withinin 5 minutes I just about wanted to drop Bill.

Everything else, really good. Neat fire extinguishers, and misc props. Would be nice if the purpose for picking them up was more explained though.

8/10 Fix those issues and you'll get easily a 9.9, not that it really matters by word.

Loading screen doesn't give the campagin much justice, though I imagine its a temp one, I hope, considering the beta tags, which in turn is why I went through the trouble of actually evaluating this, in hope that some slight improvements are made.