A humongous update has hit the ground, and is now available to download via the XTR control panel. Details are below, as stated on the Steam News Release.

Remember, if your wanting the new maps included, ensure that they are added to your map rotation!!

Added 3 Heavy unlockables

* Natascha, The Sandvich, The Killing Gloves of Boxing
* Added 35 new Heavy achievements


Added Arena game mode

* 5 arenas: Lumberyard, Ravine, Well, Granary, Badlands


Added 2 new maps

* Badwater Basin, a new payload map
* cp_steel, a community map by Jamie "Fishbus" Manson


Changes

* Added server map timeleft to upper right of scoreboard
* Added new firing sounds to The Backburner
* Removed the Custom Tab in the serverbrowser, and added the Tags field to the base Internet Tab
* Increased The Kritzkrieg's uber-charge rate bonus from 10% to 25%
* 32 player servers can now support an extra slot of SourceTV
* Made the freezecam item panel description easier to read
* Players now broadcast whether they chose a team directly or use autoteam
* Added proper handling of cart blocking recognition to Payload maps


Bug fixes

* Fixed bug where switching from flaregun-wielding Pyro to another class meant you didn't get a full ammo loadout on first spawn
* Fixed Spy watch arm not using team skins
* Fixed weapon switching preventing you from using secondary attacks for a 0.2s window after the primary became available
* Fixed players getting stuck in a bad animation state when class switching while spinning the minigun
* Fixed a loophole that allowed players to pickup weapons of other classes
* Fixed a bug that resulted in players earning more crit chance bonus in large, single damage events than they are supposed to
* Fixed an issue with the floating HUD +X health indicators that resulted in them appearing incorrectly
* Fixed a bug which caused the minigun spinning & firing sounds to occasionally stop while the Heavy was still firing
* Fixes the Loadout player model panel causing the in-game player facial animation to perform incorrectly
* Fixed spectators not having the target ID labels display correctly
* Fixed the cart alarm sound occasionally getting stuck on in Payload maps
Source