I get a lot of flak for my UI, but amongst the prefab options I see, I simply can't find one that does what I want.
I keep the unitframes, raid frames, and area map as close as possible to eye level, to minimize the distance my eye must move to look at them. This means, for example, I can see someone has aggro, or my health is low, or a debuff has gone up, much faster than if these frames were far from the center and it took me a snap second longer to change focus.
I keep certain spells on my bar so I can check range and applicability. I really wish there was a utility that could do this, but unfortunately, I've yet to find one.
I break my buffs into two sets of bars: short term self-buffs and procs go to the left of my unit frame; raid buffs and longer term buffs stay in the upper right. This is much more compact than the default configuration, and helps sort out important buffs such as Holy Shield or Sacred Shield or Heroism or Speed potions from trash like Mark of the Wild and Arcane Empowerment. Also note Heroic Presence is not displayed at all.
Buttons I may need to click - menu bar, mods, and professions - are on very small bars along the lower right. This is much more space efficient than putting them on standard size bars, or clicking from the spellbook, or crowding the minimap.
That large black spot is where Omen typically is displayed. I look at both it and Recount a great deal in combat. It's useful for me to find out exactly who is doing what even during the encounter.
People fixate on binding "1" to auto-attack. As if the gain or loss of a single bind out of 80 is game-changing. There are a lot of situations where I may want to start or stop autoattack without using a special, and it's not practical to right-click the mob because of how many are in front of me, or because I'm moving with the mouse, or manipulating some other UI element. I see this as one of those elitist platitudes (like squinting at a tank's UI to see if he's a backpedaler, or arguing about beyond marginal deviations from BiS lists or profession choices) that doesn't stand up to critical inquiry.
It's important to remember that I do a great deal more in this game than just raid as a single spec. My UI is designed to maximize functionality and information at the cost of elegance and visual appeal.
