I am a computer gamer (wielding keyboard and mouse) I think the current UI could be fine with some very simple tweaks

1. The buttons being responsive and quick : The current ones lags a little bit
2. Having all configurations and settings putting into ONE window (maybe with different tab) so I dont have to look among all those text to find the option I need
3. Whats the point to have "inventory" "gear" and "bag" with three different entry points? Can they be combined and simplified?
4. Can I drag my macro button onto my Action bar? They are kind of the same thing to me and I don't know why I have to go to two places for it
5. Drag and right click? This is probably the most efficient way of interacting with a mouse in hand... It is just very odd when I see a treasure box on screen I have to go to my right menu to open it...

You see all of these really don't require that much of graphical change to the current UI... that the screen is still clean with a lot of viewable area. They just need to organize it in an simpler and smarter way...I admit I used to play FFXI for a very long time and I compromised myself to that odd interface but I am over that phase now, NO MORE ANNOYING "Dings" tabbing through endless menus please!