Well, I actually went back and played through until I beat the tanks, which was the end of the demo. Grenades and bazookas are the way to go there; normal gunfire seems to have no effect at all. I initially thought that maybe bullets were doing small amounts of damage, but I think I was wrong there. Which is a good thing.

Couple of other points worth mentioning -

1) At one point my HUD disappeared and wouldn’t come back until I changed character. Odd.

2) Enemy corpses disappear quickly, including the corpses of tanks. I was recharging my health by hiding behind a dead tank at point when it disappeared, leaving me open to fire. Bit off that, I thought.

I also thought that maybe the different character classes would be really good in online co-op. One person hanging back on rooftops, one sneaking, one distracting the enemies by running around in full view spraying machine gun fire everywhere. No mention of online co-op in the splash screens after the demo, though, so I’ve no idea if that’s even in there.