No Spoilers:

They certainly pushed the story, action and thrill up a notch as compared to S1 followed by a lot of heartbreaks and pain.
No one knows who will make it till the end and chances are your beloved characters might just die or have a fate worse than that.
S2 proved that Humans and its greed can be far more dangerous, inhumane and ruthless than those monsters.
The acting was phenomenal, as they did manage to show all the emotions and decisions that a human can make in those drastic situations. I would say i ended up hating the humans in the show even more as compared to the blood thirsty monsters.
Both the budget and production value has increased and it shows in the series too. Eagerly waiting for S3 and the final showdown.