Via [url=http://store.steampowered.com/news/18032/]the Steam store[/url] and [url=https://list.valvesoftware.com/cgi-bin/mailman/listinfo/hlds]HLDS[/url]:

[quote=Valve]- Added new game mode 'PASS Time' to the TF2 Beta
- Check out the [url=http://www.teamfortress.com/post.php?id=17833]blog post[/url] for more information
- Fixed a crash caused by a client sending malformed network data to the server (thanks to Nathaniel Theis for this report and test case)
- Added a new hat 'The Finder's Fee'
- Will be awarded going forward on a case-by-case basis to those who report major economy-breaking bugs or remote-code-execution bugs, and provide detailed information and steps to reproduce
- Well deserved congratulations to the first recipient, Nathaniel Theis
- Fixed visual bugs caused by picking up weapons with special attributes
- Fixed the Mann vs. Machine Medigun shield not being re-created after switching away from the Medigun and back while the charge is draining
- Fixed some alignment issues in the HUD meters for the Mann vs. Machine rage knockback and Medigun shield
- Fixed left-hand view models not displaying Stat Clocks correctly
- Fixed being able to use the tournament_readystate client command when using per-player ready status mode
- Fixed seeing a HUD mp_timelimit timer for maps that don't end the round when the map timelimit runs out
- Fixed some missing VO sounds for the Demoman when laughing
- Fixed being able to use the Restore action on Killsteak Kits
- Fixed character loadout menus so they display the particle effects for all equipped Unusual items
- The Huo-Long Heater can now accept Posthumous Kills strange parts
- Updated the Australium Grenade Launcher to fix the wood material being shiny
- Updated the backpack images for the Gun Mettle Campaign Coin
- Updated LODs for several weapons and the sentry gun
- Updated Mann Co. Store prices for foreign currencies to current USD equivalents
- Updated the localization files
- Updated Koth_Suijin with the latest changes from the authors
- Added cover around the point preventing cross-point sight line
- Opened second window in point building
- Tweaked pickup amounts and positions
- Widened space between stairs to point and bridge railing to allow easier movement
- Clipping improvements
- Improved lighting in dark areas
- Fixed an issue where engineers could build on outlying islands
- Fixed an issue where engineers could trap teammates by building teleporters in spaces with restricted movement
- Fixed an issue where the spawn room doors could be held open by an opposing team member
- Optimization improvements
- Maps Workshop Beta
- Fixed a common crash when loading some compressed maps
- Fixed various issues running workshop maps on listen servers
- Listen servers no longer unnecessarily fetch a second copy of the map
- Listen servers no longer cause the client to crash upon the second load of the same workshop map
- Added -ugcpath parameter for dedicated servers to control location of downloaded workshop content
- Defaults to steamapps/workshop
- Multiple servers sharing the same UGC directory is currently not supported, and will not go well
- Added server command tf_workshop_map_status to view currently tracked maps and their status
- Enhanced handling of updated maps to ensure the newest available version of the map is always used on level change
- Improved handling of workshop maps in a server's map cycle
- Workshop maps in the map cycle will be automatically fetched and updated in the background
- Workshop maps in the map cycle will have their names updated to the canonical name once known
- Map votes now work with workshop maps
- A known issue is that the full workshop map name is currently shown instead of the friendly name
- Community request: Updated the FindMap and CanProvideLevel API for server-side mods. These functions now always expose the full workshop names for maps when known, even if not the map is not yet installed.[/quote]

Rumor has it:

- Item schema update: https://github.com/SteamDatabase/SteamTracking/commit/eb88aa3010a9819471e2320a81ef107a6c60c8da
- Here's what the Finder's Fee looks like: http://media.steampowered.com/apps/440/icons/all_bug_hat_demo_large.c4351ff20f7b7d18cfda22dea016d7838e4842c0.png

- Strings: https://github.com/SteamDatabase/GameTracking/commit/fba317e600b0432210c9a7a8d91886d7b0f59496

- Size is ~135 MB