Based on the version that I played, there is a severe lack of ammo to be found and only one game save available. While I loved playing
Metro 2033, I can foresee people getting stuck and getting very frustrated. The game autosaves for you at each checkpoint, which is good, but let's say that you just barely make it past a checkpoint with only your knife (which really doesn't work well when you're getting hit by more than one enemy). The game will save for you at that point, writing over the only game save available. Unfortunately, there is not enough ammo to be found anywhere for you to make it to the next checkpoint, no matter how much you fight with your knife. You have no option to revert to a previous save and get it right this time. You just have to start over from the beginning. But I'm really crossing my fingers that they add a multiple game save ability by the release date. Otherwise, you better hope your kid brother doesn't come along and start a new game on your profile as well, or he will overwrite your only game.
There is another element to the story of Metro 2033 that makes it much more than a typical FPS where you just run around and kill things. There are these creatures called the Dark Ones. They are possibly an evolved form of humanity, at least that is Artyom's father's theory. The Dark Ones are even more dangerous than the mutants as they don't need to be strong to kill. They simply use their minds and everyone collapses, everyone except Artyom, that is. For some unknown reason, Artyom is immune to the Dark One's power. Is he yet another evolution of human, perhaps? Honestly, I don't know yet, but I can't wait to get the book when it comes out in English next month to find out! It's been a bestselling novel in Russia for a while now.
Personally, I am dying for Metro 2033 to come out soon! We only got to play it for about 3 hours at the event, so that's just enough time to really get into it and be wanting more. If you're a fan of first person shooters, I recommend you keep your eyes open for Metro 2033.