Since you haven't play since open beta here's a list of all the changes i can think of.

-Less ui lag, very noticeable when buying/selling stuff.
- Addition of inventory sorting and increase of the size of the stack for almost every item.
- Addition of a few monsters(like mite and scorpion)
- Increase of the number of monster on the field
- Introduction of a few NMs(some on the field, some in faction leves)
- You can adjust the guildleves difficulty now.(No need to fail it it's too difficult now)
- Changes in the sp system. (Basicaly party vs difficult monster isn't the way to go now, it's linking guildleves or soloing weak monsters of your rank)
- Market wards got a few changes too. Now the wards have names that are suppose to reflect the items you'll find in and more importantly there's a search feature now.
- Addition of crtl+r for quick reply and ctrl+t for tell. However you'll have to type <t> after ctrl+t to send a tell to the character your are targeting.
- Addition of quests(not many and kind of bland for now).

That's all i can think of right now. As you can see, there's not a lot more content than before, however they did fix some annoying parts of the game like the lack of shortcut for reply and the ui lag.