I've played "through" Terraria, that is from character start to doing a run through the dungeon, twice. After that I typically get tired of it, since the RPG content runs out there (well, more accurately after several dungeon runs, but still) and since the sandboxy content is so limited. It's a lot of fun til then, though.
At some point I'd like to do a legitimate effort on hardcore; the second time I played was on hardcore but my friend and I turned it off with a character editor around the time we got to corruption, since we couldn't seem to recover our corpses. In a legitimate attempt to play on hardcore I'd probably tunnel (horizontally) obsessively, leave escape routes more accessible, etc. (If you haven't played hardcore mode, when you die you drop all you have on your person but retain your world, your character, the stuff in chests/the piggy bank, and are given copper tools. Your stuff is there to be claimed, a la Diablo, if you can actually get to it. It makes the game feel much more survivalist in feel, and was a lot more fun than vanilla until the frustration set in when we got to corruption.)
The point where I stopped last was after my friend made a harpy trap, and thus got us access to unlimited feathers and thus essentially unlimited gravitation potions...which we really couldn't do anything except just mess around with anyway.
