They are. I wasn't planning on getting the game until it hit the $20 mark or lower myself so I went and tried to find the leaks to see what the fuss was about. I found some of them before they were taken down and there indeed was a pretty massive spoiler in one video and a few things were revealed about other parts of the story which was .... very significant. They may still re-appear though.
Personally, this is a game I have zero interest in playing. I've never been a fan of horror/zombie games at all (don't hate them, just really don't have any interest), and stealthy games are often a hard sell for me.
That said, I'm sure it will be an extremely high quality adventure game regardless whatever plot choices they make. After all, it's Naughty Dog, and the journey will be the key.
The part that impressed me the most about the first one was the characters, so I am interested to see what they do with them. I will give zero impressions from the leaks, though, just to be safe. Even with the protection of spoiler tags, I know how much this game means to some people.