This new service called Steam Cloud (very inventive) will be able to store keyboard and mouse related settings as well as paint tag settings. This is a great feature if you are in the habit of playing your Steam games from different systems. The saved setting will be automatically applied as soon as a user launches a game through their Steam account and any changes made will be saved to the Steam servers.
Steam will make this available to all game companies using Steam for distribution free of charge and will go live with the upcoming demo of Left 4 Dead.
Read more here.
The Steam Cloud will "just work," meaning any user changes to their game options will propagate to the Cloud by default. Upon logging into Steam from another PC, these settings will be brought down from the Cloud and automatically leveraged by the game. Any configuration changes on this second machine are then synced to the Cloud for future sessions.
Steam Cloud will be available to all publishers and developers using Steam, free of charge, and Valve will add Cloud support to its back catalog of Steam games. Cloud services are compatible with games purchased via Steam, at retail, and other digital outlets.