FROM STEAM NEWS (Source):

Updates to Team Fortress 2 have been released. The updates will be applied automatically when your Steam client is restarted. The major changes include:
Team Fortress 2 

  • Added the Mann-conomy.
    • Added 65 new items (hats, weapons, tools, minigames, gifts, crates).
    • Added the Mann Co. Store & Catalog.
    • Added Trading.
    • Added Item customization.
  • Additional TF2 features
    • Added new auto-team-scramble system:
      • Set mp_scrambleteams_auto to 1 (default) to automatically scramble the teams if the criteria is met
      • Set mp_scrambleteams_auto_windifference to set the number of round wins a team must lead by in order to trigger an auto scramble (default is 2)
    • Updated how Spy disguise targets are selected to more randomly distribute the selections
    • Fixed the FreezePanel background not using the correct color if you were killed by a player or building on your own team
    • Server browser tweaks
      • It will now encourage you to add servers to Favorites or Blacklists after you have a good/bad experience on them.
      • The Server Browser now automatically closes after successfully connecting to a server (opt-out via the Options-Multiplayer->Advanced dialog)
  • Achievement tuning
    • Demoman achievement “The Stickening” changed to 3 from 5.
    • Heavy achievement “Krazy Ivan” changed to 50 from 100.
    • Medic achievement “Consultation” changed to 3 from 5.
    • Medic achievement “Peer Review” changed to 10 from 50.
    • Medic achievement “Placebo Effect” changed to 2 from from 5.
    • Medic achievement “FYI I am A Medic” changed to 1 from 5.
    • Medic achievement “Family Practice” changed to 5 from 10.
    • Soldier achievement “Geneva Contravention” changed to 3 from 5.
    • Scout achievement “Strike Zone” now counts assists.
    • Scout achievements “Fall Classic” and “Foul Territory” are fixed.

Engine (CS:S, DoD:S, TF2, HL2:DM)

  • Added sv_alltalk to the list of convars that are checked for the sv_tags list.
  • Fixed a model instance crash.
  • Removed engine ConVar “r_ForceRestore”

Other Games
Half-Life 2: Deathmatch
Updated to run on the Orange Box engine with CS:S, DoD:S, and TF2

The latest Team Fortress 2 patch has dropped! Here’s a quick analysis of the changes:

Added the Mann-conomy. This covers a few new elements to the game. First, they’ve added a brand new in-game catalog that allows you to use your “Steam Wallet” to purchase items. This is a novel idea and makes financial sense considering how long Valve has been supporting this game. Note that the Steam Wallet encompasses all of Steam and not just Team Fortress 2. This is similar to Microsoft Points for Xbox, except Valve uses real money.

Next is the implementation of player-to-player trading. This allows you to trade or gift items you’ve found or crafted to another player. Pretty neat addition and about time. They’ve been talking about it for ages. Also note that at the moment you CANNOT trade or craft purchase items.

Item customization is another step in adding more personalization to your character. Certain items, and I believe this just applies to purchase items, can be renamed and colored differently. Kind of a cool idea, but a few in the forums mentioned how this has “ruined” the art-style. I suppose time will tell.

Added new auto-team-scramble system. I have a feeling this change is going to be a hate-love relationship. On one hand scrambling teams is a great feature because it balances the game and ensures a fair match, but how annoying is this going to be for friends who want to play together. Granted servers will need to enable this, but I have a feeling a decent number will since people bitch about unfair teams all the time.

Server Browser Tweaks: This will require some testing, so I’ll hit up an update once I get a chance to play, but it sounds like there might be some serious potential. Server browsing for the most part hasn’t changed a hell of a lot since even Counter-Strike, so updating the interaction, interface, etc. would be a breath of fresh air.

The official MANN-conomy update page

Helpful resource for understanding the new update: MANN-conomy FAQ