Byzantium has officially been rolled out on the Ethereum blockchain. At 05:22 UTC the fifth hard fork on the block chain (with a market cap of $30 billion) went live. The hardfork was designed to address and improve numerous aspects of the blockchain, including security, speed and scalablity.
Price action was pretty volatile just prior the fork, but immdiately after ETH jumped approx. 2% to $348. Next in line is the planned upgrade code names Constantinople.
Developers had seriously considered postponing the Byzantium fork, but with that being a complicated process, they decided to roll with it. Even though the hard fork is live there's still concerns that their could be a network partition due to a consensus issue with a version of Parity that was released just prior to the planned fork.
So far there have been no notable issues and developers have been seen celebrating on Twitter and other social media outlets.