Valve has announced that the Steam Cloud service (announced back in May) will finally make its debut later this week, alongside the demo of Left 4 Dead, which will be available on Thursday to those who preordered the game and on November 11 to everyone else.
The new service will allow gamers to upload things like game saves, mouse and keyboard settings, and player profiles to Valve's servers. The idea is that when you login to your Steam account on another PC your system will automatically set itself up in line with all your previous configurations.
Left 4 Dead will be the first game to support Steam Cloud, with previous releases scheduled to adopt it in the near future. In addition, Valve stated that the service will be available for free to all publishers and developers who wish to include such support in their releases, so hopefully we'll see the system spreading soon enough.