Once, when experimenting on my holy paladin (I'm a dirty traitor, I know), I healed through an entire heroic dungeon with my user interface disabled. Matticus had recommended the exercise, as it allows you to focus on what's happening and your surroundings instead of little green bars. The experience was interesting, but I simply couldn't handle it. I'm an information junkie, and I want to know everything there is to know all at once. Why? Because knowledge is power, knowledge is the food of the soul, and knowing is half the battle.
With that said, there's still such a thing as too much information. I can set up my UI to have all sorts of numbers and statistics displayed everywhere, but it's not valuable unless I can interpret them. When you're in a high-stress situation like learning a new boss fight, you want to spend as little time as possible worrying about your UI. A good UI should make your rogue easier to play, not harder.