Well, there's a lot to like about it, and a few things to dislike about it.
Negative:
-A lot goddamn harder. Chests tend to be either in the center which is usually camped by people in full iron, deep inside dark buildings where mobs are spawning everywhere, or take considerable parkour skills to get to. The first night can be absolute hell, since safe spots are harder to find. Even food can be a bit difficult to get to.
-Harder to find other people. The map may be as big as the first, but the abundance of walls and tall buildings really don't halp people find each other.
Positive:
-A lot more detailed. The first map was pretty much a forest and some islands, with some ruins/secrets every once in a while. Here, there are like 50-100 different buildings, most of which have secrets in them, and some other odd bits too, like the subway.
-Fights are about twice as cool. The new terrain really makes fights more intense. I remember one where 2 people were trying to climb vines and hit each other off of them, and whenever one would start falling they'd manage to grab back onto the vines. There was also one I had where I was near the top of a cathedral, and some guy tried to hit me off. I managed to knock him off, however, and he landed on the staircase not entirely dead. Just when I thought I could take a breather, I realized too late that he was aiming a bow at me, and I died. Fights like this were unheard of in the first map.