The game is really buggy.
Hard mode enemies in mushroom biome,
Multiples of the same NPC moving in,
Enemies spawn in your house,
Enemies walk through closed doors,
Lights keep 'popping' into view (torches switch off when off screen, and it's really jarring when they pop back into view)
Regardless of it clearly being rushed out for Christmas, it's still Terraria. It's still a great game, and I must admit that I like what they've done with the UI. The world size is what's annoying me the most.
Also, I've been playing for about 10 hours or so, I've got full health but still, the eye of Cthulhu hasn't challenged me?
Not sure why.
And saving your game takes AGES!