From reading the forums, from chatting to guildies and from personal experience, I think we can all agree that the DDO UI is an abomination.
Even with the recent tweaks (which have helped, but in a very badly-thought-out way) it is still a real mess.
I originally came from Everquest, which started with a very old school UI http://www.tentonhammer.com/image/view/65353/preview
When the expansion Shadows Of Luclin, SoE included a complete revamp of the UI, coded in XML, which gave players the ability to dramatically change the appearance (and a certain amount of functionality) of the UI (see samples below).
http://www.eqinterface.com/downloads...now=1360663937
http://www.eqinterface.com/downloads...now=1360663968
http://www.eqinterface.com/downloads...now=1360664020
It was also possible to precisely define individual window locations etc so you didn't have drag windows into almost-kinda-the-right-position-at-least-until-you-window-out.
That was ten years ago.
Seriously...