Rockstar has released patch number 6 for the PC version of GTA IV which features a large number of bug fixes and additional features. The patch is available through Games for Windows LIVE and a standalone downloadable version with be available soon. The majority of these new features/fixes are already present in the PC version of Episodes from Liberty City.

Rockstar Games Social Club

• Remove Rockstar Games Social Club application
  
• Separate RGSC application no longer required to launch game
  
• Social Club login now occurs during the launch process
  

Shadows

• A new, less memory-intensive, and better-looking scalable shadow solution has been implemented
  
• Enhanced Night Shadows added with user-selectable level of detail (replaces Shadow Density)
  

Performance

• Rendering optimizations have been made to improve performance, particularly when enabling shadows
  
• User-configurable graphics settings have been added for shadow control
  
• Improved memory management
  

Multiplayer

• Enhanced security to isolate users from cheaters and hackers
  

Episodic Content

• Provide in-game support to purchase "The Lost and Damned" and "The Ballad of Gay Tony" (Not available in Russian/Japanese Versions)
  

Bug Fixes

• Vehicle shadows re-enabled between 8pm and 6am
  
• Fix floating street textures
  
• Pedestrians in vehicles appear further out from the player to allow for long range sniping
  
• The Moon has been implemented with simulated lunar phases
  
• Fixed garbled text in Japanese Multiplayer menus
  
• "RESC 10" error fix for specific hardware configurations
  

In addition, Episodes from Liberty City players are also getting a small update (1.1.1.0) that will improve memory management and address a hardware configuration error.