Things like random fuse locations, store alarms, the light switches and radiation make it stand out from other campaigns.
New sounds and textures.
Awesome safe room music.
The tank music starts on a delay. (this might just be in my game so I won't remove any points)
This is a great campaign, and being a fan of S.T.A.L.K.E.R and Metro 2033 made it even more fun. I didn't notice any bugs besides the tank music. My game did crash around the start of chapter three the first time I played it, but when I relaunched it everything was fine. Hope to see this added to the official campaigns like Cold Stream was.