EA/DICE has announced that a major client update for the PC version of Battlefield 3 will be made available on November 21st at 11:00 PM PST and that online services to be down for two hours. This also includes a server-side update for all platforms as well.
As promised, fans will see "improved polish, stability, weapons balancing, squad control functionality, user interface enhancements, and several feature enhancements that address feedback the community has provided to date."
While this update is only going to affect PC users, DICE did announce that the PS3 and Xbox 360 patch will be available at a later date. DICE explained on their official blog that console patches "tend to take a bit longer due to the console certification process." They did make it clear that this update "will not change anything in-game".
As for what the patch will update, DICE provided a full run-down of both the client-side and server-side updates. A full list of the changes is available on the Battlelog.
Client-side Update Improvements
• General performance and loading time improvements
• "Black Screen" fix for an issue occurring on some PC configurations
• Stereo and rendering support for Nvidia and AMD graphics cards
• Fixed several crashes that occurred when joining multiplayer and co-op sessions
• Fixed a problem with high speed mouse movement (aka "negative mouse acceleration")
• You should no longer be able to damage a friendly vehicle when sitting in an open position
• Grenades now drop to ground if you get killed while attempting to throw it (dangerous in Hardcore mode!)
• You should no longer spawn too close to enemies in TDM, SQDM, or Conquest
• A large number of damage and range tweaks on a number of weapons to fine-tune overall balance in the game
• Added round duration and ticket summary at End of Round screen
• Fixed a problem regarding key bindings while playing
• Significant changes to the Join Squad interface, detailed at the bottom of this post
Server-side Update Improvements
• EOD Bot exploit fix
• Several crash fixes
• Anti-stat padding measures taken, disallowing ranked servers to run obscure settings
• Improved team kill kick configuration
• Support for unranked servers. Unranked servers do not report players' scores to Battlelog, but server administrators can freely control all settings
Some more changes can be found on the official Battlefield Blog.