This may be a very minor thing, but needs to be mentioned, I love, love, that there is a toggle for having headgear shown or invisible on your avatar. Helmets never seem to look right on my character at all, and when I found out you can have headgear on, but keep it invisible, I about had a heart attack because that was something I really wanted back in my XI days.

My Elvaan DRK was the same style Elvaan as my Elezen, and being in the DRK armor without the helmet on, looked far more bad ass than with.

What's your favorite thing about XIV's UI?