Next week's Steam update will include significant changes to both the user interface and the functionality of Valve's online distribution system.
According to a press release from Valve, the update will introduce guest passes, background client updates, a new user interface and a favorites system for the games list.
Guest passes will operate very much like the trial passes for games like World of Warcraft. A player who already owns a game on Steam will be able to offer their friends a free, limited-time trial period. The first game to offer this feature will be Day of Defeat: Source.
Background client updates mark a significant change in Steam client operation. In the past, updates have been downloaded and applied only when the Steam client was restarted. Now, updates will be downloaded automatically, and the user can decide when to restart and apply the changes.
The update is due sometime next week.