The smoke nads are fun to use. The cloud of smoke starts out small and slowly grows to fill the entire area. It takes quite a while for it to disipate. You have to be very careful walking through it. When I would try to 'rambo' through it, a guy would jump out and start hitting me with the butt of his gun.
Fun demo. I finished it on the normal difficulty level in about 20 minutes. It would be a 'must buy' PC game if I weren't getting the 360.