I had a lot of fun with this demo. I do have a couple critiques.
for one: the music (while good) was loud, and I wanted to have a slider just to turn the music down without having to turn down the master volume.
second: The AK-47 felt very underpowered. I didn't use it much. The recoil was all over the place. The pistol did more damage, and was a lot easier to use.
Third: that third area... a notice that we either needed to survive or wait for the bridge would have been nice. I had no idea where I was going, or what I was supposed to do.
All in all, This was a very fun experience.