Finished the game yesterday evening after a break from playing, and I loved the game. The only problems I had with it were the difficulty spikes, which were a bit extreme at times, but that's all. Not even the heavily scripted stuff bothered me much. Maybe because everything was so well executed and because the setting kicked some serious butt.
Also, all characters are well-made and very...real. Even the narrator's voice on the loading screens is great, very bleak and a little fearful. The world of Metro just WORKS and it has to be said that the graphical design team did a stellar job translating it into a video game. As mentioned before, the military-grade-bullets-as-currency adds an interesting twist to something as simple as ammo management, and the gas masks, night vision goggles, flashlight charger, wristwatch timers and all that jazz are very well integrated into the rest of the game. I also love that when examining bodies of people you actually have to 'pad' them down for stuff in their seperate pockets. Nice little detail.
One thing that stood out for me as well was the difference between the monsters and the human enemies. WHile they are COMPLETELY different opponents, they are both lethal in their own way. Humans tend to be relatively squishy but you often fight them in groups and they make up for their weakness by having strong ranged weapons and being smarter than most. The beasts are generally either very strong single enemies or swarm-like groups, and both are really scary.
As for the ending:
I tried to come to an understanding with the beasts, but I didn't get the option. 
Research shows that you have to do a lot of stuff in a particular way during the game to unlock that possibility, so I guess I didn't do them. Ah well. So yeah, I nuked the beasts' homes.
Research shows that you have to do a lot of stuff in a particular way during the game to unlock that possibility, so I guess I didn't do them. Ah well. So yeah, I nuked the beasts' homes.Can't wait for Metro: Last Light in any case.
So it wasn't entirely my fault!