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