Steam has released an update to its chat system. Steam has made the new Steam chat features, which have been in beta since June 12th, available to all Steam users. The all-new friends list and chat system makes it easier to chat and play games with your Steam friends. They'll continue to improve the new chat system based on our feedback and requests. They've already started working on making it easier to chat from anywhere with a new Steam chat mobile app for iPhone and Android devices.
Check out the announcement page to learn more about the new features and what was added/fixed during the beta period