There are numerous topics so I will list them, and you can search the page for them.
Max HP Pots weight nothing. Grab a ton if you want them.
Farm wagons move fast and can carry significantly more than normal. Load them up.
Guild: To create a Guild, you have to be above level 45.
Guild Quests can be done by 1 player.
Junk: Junk drops have good value. At AP 100, the mobs give 10,000 per drop. At AP 270 the mobs can give 55,000.
Doubles: Many end game mobs are doubled and tripled for grinding fun. Be careful.
Classes: Classes have been tweaked a little bit. You will notice some fun things (ex: Wizard has a FULL BLOCK when backing up)
NPCs: Not all NPCs are spawned all of the time. If you walk up and one is missing, type .pc sync (This significantly lowers lag).
World Bosses: World bosses have been adjusted so anyone can fight them.