We've written about ERC223 token standard before and why we chose it for our STN token. ERC223 makes writing smart contracts that work with tokens much simpler, more efficient and more secure. Unfortunately, most of the smart contracts that are written today have to comply with the dominating ERC20 standard if they want to get a real market share. Namely, there aren't any decentralized exchanges for ERC223 tokens on the market yet, although Bittrex already supports the standard.
This is a companion discussion topic for the original entry at http://rados.io/erc20-erc223-upgrade-path/