New races, each avaliable for a season (frost giants in winter, centaurs in spring, goblins in autumn).
New limited race (azuretouched). Kinda like aasimar but more human than angel/archon.
ABS re-done (opinions vary on the new system).
Edgepoints nerfed.
Some old areas re-done (Emerald forest, Arial city, Strange island, Galadon somewhat). Some areas replaced (whitecloaks by siege encampment).
Lots of events. Two "Nights of 100", among others, and two campaigns that allowed a bunch of people to play pre-gen characters related to each other, with ongoing imm-driven storylines.
Edgepoints nerfed.
Scarab takes Scion's place.
Outlander dogma on orcs and dwarves changed somewhat.
Oddball combos occasionally allowed to roll by immortal consent. Dwarf transmuter, felar paladin, duergar ranger etc.
Bunch of new imms.
Bunch of new mechanics: harder to walk or fly if overburdened, mob-assisted PK wins count properly, etc etc. See announcement forum.
Bunch of imm answers to questions and requests. See Santa Zulg and Twist the Season to be Jolly.
Also, I got a PK win. Before edgepoints were nerfed, that is.