Enough, we want a client-side user interface!
Even after UI lag fixes in previous updates, UI in FFXIV is still so much less intuitive and responsive compared to many other MMOs out there, and I believe this contributes significantly to the feelings of slow, boring, and sluggishness that people are experiencing when playing FFXIV.
A client-sided UI should be the utmost priority tweak for the UI, before anything else.
I know it will take a long time to do this, and that is exactly why you better start working on it now, SE.
I am also sure that the community will greatly value feedback from the development team on this matter.