"Sword beats paper, get one today."
Good:
-$10 price tag. Enough content to keep you busy gathering loot for at least 20-30 hours.
-They've already patched the game 5 times since it's May 16th release and each patch has added a very significant amount of content.
-Co-op or PVP multiplayer capability is very cool.
-Absolutely huge randomly generated environments.
-A ton of craftables, collectables, and ore types that you are constantly rewarded with. You can build some pretty neat bases with patience too (castle, treehouse, underwater base, sky base, lava base, etc).
Bad:
-There isn't really a final boss or enough endgame content that will continue to test players with the best gear. Skeletor may scare people off with bad equipment, but I think I burned 2 maybe 3 potions taking him out. Other than multiplayer or base building, I have no reason to continue playing the game.
-The tutorial is... well, there isn't one. There are some good wikis on the internet at least.
-It can be discouraging getting killed over and over by zombies and slimes at the start of the game, especially if you have no idea what you're doing.
-Constant respawns of certain mobs are horrendously annoying, especially with knockbacks in effect. Goblin Armies, Fire Imps, and Meteor Heads are harder than the bosses if you think about it.
If you enjoy 2D RPG action games or just being creative and doing your own thing, you owe it to yourself to try this game out. This is definitely a contender for the best deal I've ever gotten for $10.