I've played with the new UI on the test server. Aside from being very ugly looking in its current state, it has a lot of promise. I like being able to have different screens open at the same time especially. But currently, it's extremely unfinished and only like half the UI text is translated in the English client. Maybe some people don't care, I don't know, but it's not worth developing if they are going to give it such a low priority that it will never be finished.
I remember when this was first announced and I was really excited about it. It was brought up around the same time as Cait Sith (which we FINALLY have). I would reeeeally like to see it finished. Please?
(though as an aside, one of the things that bugs me most, especially after being so used to XIV's mouse input, is that the mouse control in XI still hasn't been addressed. Aside from clicking on UI buttons it's still worthless- the method by which the mouse controls camera and character movement is about as clunky as it could possibly get, with movement of either being limited to 8 directions despite the mouse being an analog input device capable of fine movement in any direction)