Wow, wow and wow - this game is amazing so far. A busy weekend so I was getting all my playtime in during the wee hours of the morning (the best time for this game coupled with headphones) and I'm only in chapter 9 of 12 after a solid 14 hours.
Some elements of the game can break the immersion but it's been a rare occurrence (visibility is only based on the player character hence you sometimes see the AI move clearly into line-of-sight and trigger no response). The graphics are mind-blowing, characters and and interactions exceed Uncharted and combat, with both infected and humans, is seriously tension-inducing. I've never spent so much time physically twitching with anticipation or dread, waiting to see the outcome of a situation.
The story fluctuates between incredibly bleak but has it's moments of joy. The game forces you to grow attached to characters and leaves you terrified at the outcome. Sometimes its as tragic as you feared, other times you're overjoyed that things have simply remained peaceful and no lives were lost.
While the game is still strongly linear, areas are more open for some scavenging. The environments themselves are incredible - I can think of few games that make you feel like you're moving through a real place rather than a videogame level dressed up as real place.
Combat allows for stealth, gunplay or a mix of both. The further you go into the game, the more often you'll be forced into combat in the story and even in these sections, gunfights can be terrifying as a few bullets will end you and a good hit will knock over your character (think RE6 but done much better).
Anyone with an interest in a great survival game, a great story or just an all-round experience should give this game a try.