Here's the Breakdown.
There will be 5 New maps.
There will be a new Payload Gametype that has a map joining with it.
The heavy update will be next.
Meet the team video.
Heavy Achievements.
New Game Modes
Steams says, "the largest update to Team Fortress 2 since it was first released," and "make the Heavy more viable when he has no Medic to pair with.".
Steam via
Kotaku
Team Fortress Tuesdays just got
oh so much better.
This was part of my reason in my Valve Instant Replay post.
DO YOU NOT SEE HOW FUCKING AWESOME VALVE IS?!?! 
Scrixx's blog
Follow
RSS
Contact
*pisses pants*
*please note that the post above is meant to be read in a tone of sarcasm. thank you
Who's the next member of the team we will be meeting? Please say it's the Medic!
I'm extremely interested in the weapons the Heavy will be getting to make him more viable without a Medic. So far my only guess (and hope) is a gun that shoots fists. That's right, shooting fists, you know you want it.