Updates to Team Fortress 2, Counter-Strike: Source and Day of Defeat: Source have been released. The updates will be applied automatically when your Steam client is restarted. The major changes include:

Source Engine Changes (CS:S, DoD:S, TF2)

• Optimizations to multi-core rendering
  
• Removed -heapsize command line argument. Some detail: This command made sense in Half-Life 1’s memory manager. The current engine manages memory in a way that doesn’t need it specified. Under some circumstances, specifying a non-optimal heapsize causes crashes and/or reduced performance
  
• Fixed an exploit that allowed people to send fake VAC messages to clients