The game client is now a 64-bit program. It runs smoother, opening the bag no longer stutters, and the old memory limit is gone. It needs 64-bit Windows; everything else comes with the update.
Gear got a rebalance. Armour gets stronger with its level, gear stats follow the item level more evenly, and most armour and accessories can now be worn by every job. Bonus stats on newly dropped gear now depend on the item's level.
A few attire items no longer drop from monsters or come from a crafting trader.
Start the launcher to get the update. If your launcher was already open, close it and start it again.