With this Steam Client Beta, we've also made some changes to how we organize and announce beta updates:
Added a new Community group for following and discussing Client betas:
http://steamcommunity.com/groups/SteamClientBeta
When a beta update is available, the update dialog will now show Steam Client Beta changes instead of showing only the released client changes.
Client changes:
Offline messaging: You can now send messages to users who are offline. They will receive the message when they next log in.
Opening a chat dialog with a friend will show some recent chat history
A web chat interface is available, you can find it by navigating to the Steam Community Friend Activity page in your web browser. NOTE: during the beta, web chat users will show as "Online on Mobile Device".
fixed several issues with scroll bars in the store and community views
Added a caps lock warning indicator to the login dialog password textbox
Removed "/me" chat command, which allowed some users to modify the color of their chat text
Fixed forum links opening in external browser windows
Reduced retail install time when reading from optical disc on Windows XP/Vista
Added support for better content sharing between games
Mac: greatly reduced CPU usage and power consumption
Mac: fixed command-W and other keyboard shortcuts
Mac: fixed bugs with window management and the Window menu
http://steamcommunity.com/groups/SteamClientBeta#announcements