As of Version 0.13:

• You can Build grids alone or with friends via direct connect IP (currently requires port forwarding, I'm looking for a solution)
  
• Build your map with a large selection of blocks to work with, and many more coming!
  
• Place special blocks such as spawn points, jump pads and teleporters
  
• Place Guns, Pickups, and Ammo spawners
  
• Use wires to connect doors to buttons, activate platforms or lasers, and generally create puzzles!
  
• Launch the grid you're working on into Game Mode and play a match with your friends!
  
• Customize your character with different colors and armor pieces
  
• Change the time of day, world color and game properties from the world node
  
• More stuff I've forgotten to mention!

Big future plans:

• Public hosting: Host a map you made in a public lobby and let everyone join you in your own map!
  
• Grid Sharing: Upload your gird for others to play and rate
  
• vehicles!
  
• Waypoints for races, navigation or as an end for your challenge maps
  
• team based power cores and receivers for CTF style games
  
• Even more stuff I've forgotten to mention!