Terraria's got a lot of item customization and an actual storyline. There are even World Bosses in the game. Overall, it's just a more completed version of minecraft. If Terraria wasn't 2d and was more like Minecraft, I'd never leave it.
Laaaaame. I had a huge project going on in that one. I would have liked to see it completed. I was on two other servers with two different groups of friends, but the same thing happened to them and both servers died. A few of them have moved to Terraria now. I like it, but there's something special about Minecraft, which sucks because Terraria seems to be better in all the other areas expect 3dness.