It was definetally better than the first one. It was very well designed and for once levels in an FPSC game were nice and long.
I won't go through the levels individually and describe my experiences in them (mabye later) but I will give you a list of things that I thought needed work.
From the start we get a conversation with the American. If he has a name I didn't catch it as the voice overs were so quiet. I found myself having to turn my volume up and down to catch each part of the dialogue. It got to the point where I just got bored of it and decided to move on, ignoring it completely. You need to get louder VO with better quality and in shorter bursts next time.
Guns in general were pretty nice, I enjoyed them although again, the TNT texture seemed very out of place. Also the laser gun you got later in the game (can't recall the name) really needed some animations, even just the default assault rifle ones would have worked. It also seemed a little out of place as I think I came across it once and that was it.
One major let down was sound. This game was crying for some atmospheric ambiences and twisted, 20th century music. I was really disappointed at how little sound was used. I loved the little trench parts in the first level but you could have made them epic with the far away churning of motors from the airships, perhaps an echoey voice over a loudspeaker, mabye a little gunfire.
I wouldn't have minded some more enemy types. While the bioshock dudes and guards were cool have you ever considered different classes of guard with different uniforms?
The final level was a disappointment for me. The whole game was leading to this skylift and I was looking forward to seeing how you could implement it. When I first saw it I thought: "Wow! This could be excellent!" Then it just ended. That level was begging for a more epic/dramatic rise in the skylift with sights of the city etc. It would have been tough but it could have been done.
My final point is that nothing much happened. It stuck to a formula of "dialogue/fighting/small puzzle". For a game with 8 levels it really needed some nice scripted events and such.
Finally a glitch: In the 4th level at the start there are turrets with invisible segments around them. From the second level (I climbed up the boxes) I managed to jump onto one of the turrents and from that jump down onto one of the turrets on the first level. I was then trapped because of the invisible segments. I suggest you rethink that part
On the other hand, what AI were you using? You had up to 3 enemies firing at once and they were all responsive. How did you manage that?