User summary:
The December 17th playtest package supported levels up to 20 for the first time. There were significant updates and changes to almost all of the files included, and a new adventure was added to the pack.
This playtest packet included:
Playtest Packet (2012-12-17)
D&D Next Playtest Update ("Read First", 3 pages)
How to Play (24 pages)
Creating a Character (5 pages)
Classes (28 pages)
Races (8 pages)
Backgrounds and Skills (11 pages)
Specialties and Feats (11 pages)
Maneuvers (4 pages)
Spells (35 pages)
Equipment (11 pages)
Magic Items (30 pages)
DM Guidelines (14 pages)
Bestiary (95 pages)
Reclaiming Blingdenstone (not updated, 40 pages)
Dungeon Module B2: The Caves of Chaos (not updated, 23 pages)
Dungeon Adventure X1: The Isle of Dread (not updated, 44 pages)
The Mud Sorcerer's Tomb (34 pages)
Character sheet (not updated, 2 pages)
Pre-gen: Dwarf Fighter (2 pages)
Pre-gen: Elf Wizard (2 pages)
Pre-gen: Halfling Rogue (2 pages)
Pre-gen: Human Cleric (2 pages)
Pre-gen: Human Fighter (1 page)