The fact that opening up a backpack opens it OVER YOUR INVENTORY instead of to one side or the other.
The fact that there's no delay on popup text, meaning that while browsing your inventory, you have 2-3 items blocked by a popup text box at all times.
I give you the backpack.
The popup however... no. I don't want to wait 2 seconds or something for every item popup to appear to see what's better than what or what has what status effects. That's far more annoying that the current system, believe me...