Hey, long time lurker, 1st. time poster. Would like to say thanks to the people posting in this thread, it served as a great source of inspiration.
Anyway, this is the current version of the UI layout I've been using for almost 2 years.
General idea is to present as much information as possible while keeping the screen clean.
Bright colors are used for the important elements (unitframes, debuffs tracker, cast bars) to immediately draw attention to them, while keeping the other elements small/subdued.
Addons: STUF, Dominos, ractionbuttonstyler, Grid, ForteXorcist, Skada, TipTac