From the blog "Sandbox Update Notes"

+ Added support for local and dedicated server multiplayer + Biome, humidity, altitude, and temperature information can now be seen for the given chunk within the F3 screen + Chunk borders are now shown in the F3 screen + Added Tile Entity support (currently only includes trees) + Added support for Linux (32 and 64 bit) + Added support for player profiles + Added support for characters - characters are used to separate stats, inventories, etc. across worlds and servers + Added paus