Valve's Steamworks game development tools that reveals a couple of new features that were not previously announced. One big one is new support for in-game microtransactions. Steamworks has now been upgraded to allow developers to use the tools to support such transactions. Players can now purchase in-game items within their Steam account.
Valve has also upgrades their Steam Cloud feature to allow for 100MB of data to be stored in the server per game (previously the storage capacity was a mere 1MB). There also also some interesting Steam stats in the PDF including the fact that there are 20 petabytes of data delivered via Steam each month (which, if you are unfamiliar with "petabytes" , is a lot. Look it up).