From seeing certain threads, hearing different podcasts (including Vinny on the Bombcast), and other stuff like that while I was still playing the game, I thought this was going to be really dark, especially the ending. I'm not saying this was blue skies, but I don't think anything THAT dark happened. I like the grayness/selfishness in Joel's final choice, but the world is screwed anyway. Unless Ellie could bring back the infected I don't see the big deal, since they said "vaccine" later in the game and not "cure", I doubt they could do that.
Either way humanity would still have to fight the infected and themselves for resources. I guess after "a certain wedding" a few weeks ago on TV, I classify dark endings a bit harsher. I would definitely say The Walking Dead (the 2012 video game) is darker and more unsettling than this to me. This is a great game, easily the best PS3 exclusive... I just don't get all the talk about it being dark/twisted. Also, it seemed like David was going to strangle Ellie in the burning bar, not rape her, which she seemed to imply.
I'm surprised that they had such an open ending. This feels complete but it definitely seems like they want this to be a series. I'm glad Joel survived since that would've been a cliche for this type of story.