To each their own, I suppose. I liked the NPCs, idea for economy seemed brilliant and the atmosphere was great. Gameplay was nothing stellar, but I don't play FPSes (other than ArmA) for gameplay. Maybe if the same story was told differently, it's be average, but something in a way it was told just got me. I especially liked the beginning, later (after Polis station) it got somewhat weird, but still enjoyable. I don't have much to say for the puzzles, but they felt allright. Afterall, strange visions inside your head are rarely coherent. They felt right and weren't too difficult.
As for level design, it was indeed quite poor gameplay-wise, but very realistic. Let's face it, Moscow metro wasn't build with such events in mind, and it certainly felt like it. I'm not sure about auditory directional handling complaint, I didn't pay that much attention to sound system, but with my 5.1 headphones, it sounded really good. It also had amazing graphics, which I was able to experience in all their DX10 glory (decision to switch to Vista finally starts paying off).
Note, the above is coming from a guy living at the doorstep of former Soviet Union. Moscow is much closer to me than Las Vegas, both culturally and geographically. One thing I liked about Metro is that it was very Russian. I guess that somebody living in a different place might have different feelings about it.
Also, I wonder if you noticed a Discworld shout-out (because there's no way that could be accidental, I tell you).
