It's amazing. Difficulty modes, online multiplayer (Co-op, PvP), a gigantic selection of items, fast transit options, flying, lazer beams, robot skeletons, bunnies in slime costumes, Excalibur. There's so much to do that it's easy to start one thing and get sidetracked for 40 or 50 hours on something else. The NPC mechanic is one of my favorite of all these sandbox builder games, and it's rarely replicated at all let alone as successfully as it is here.

If you like sandbox builders, creative mode, survival mode, tons of gameplay depth, tons of construction depth, or just really great friggin games you absolutely should play Terraria. Right now. Go.