Left 4 Dead has been updated to include a lobby browser. The lobby browser (under Play Online) will show you a list of optimal games available for you to join. The browser pares down the thousands of lobbies and games currently being played to show you the best list of games available to you. This list includes official and add-on campaigns, including add-on campaigns you have not yet installed, making it a great way to discover them. You can filter by difficulty, official and/or add-on campaigns and by lobbies and/or games in progress. The specific changes include:

Left 4 Dead

• The Play on Steam Group Server screen now displays which Steam group it's searching while updating the list
  
• After calling a vote to change difficulty in game it is now correctly updated in matchmaking
  

Add-on Campaigns

• When downloading a new version of an add-on and installing it (by double clicking the .VPK file), it will now correctly overwrite the previous version, even while Left 4 Dead is currently running
  
• Addressed a crash when two mission files with the same name are installed
  
• Steam Group Servers now will now correctly offer download links when running add-on campaigns
  

Server

• The server will now warn if the public or private tags exceed their limits. Public tags are limited to 63 characters. Private tags used for matchmaking are now limited to 1024 characters. Note that the private tags include the name of each add-on campaign installed on the server, so an excessive number of add-on campaigns can hit this limit
  

SDK

• The VPK tool should be able to handle campaigns larger than 500MB now
  
• You can now drag and drop or pass a VPK file to the vpk.exe tool to have it extract the contents of the add-on to a folder. This mirrors the functionality of passing a folder and having it create a VPK file
  
• Detail.vbsp and lights.rad have been added to the distribution