Sorry for the jumbo image, didn't know how to thumbnail it. Direct link @
http://www.ramenite.net/wowui1.jpg
I spent 70 levels basically staring at my bars to properly time my cooldowns. My goal was to be able to maintain situational awareness by keeping my eyes centered and getting all the info I need without looking around too much. I'm 100% keyboard+mouse buttons user (no clicking ever, just personal preference). In addition I wanted a mostly empty interface when I'm not in combat. BTW Omen is right below the center of my screen when I'm grouped.
I've got a few dozen addons (123 folders worth). Here's a few:
X-Perl: For the raid party/target/raid frames
Recount: Damage meter and analysis tool
Titan Bar: I could never get into FuBar
Prat: Chat mod & home 11.2 billion options for all 2-3 things I actually use
Bongos: For the bottom bars, love the customization and auto fading bars. my WoW menu and bag bar auto-fade to 0% on the right side of my screen.
Chinchilla: Best minimap mod ever. Tons and tons of features.
Minimap Button Bag: For a cleaner look.
Cartographer Routes: Those lines on the minimap are routes between each node in the zone.
Metahud: At a glance health and rage info, slightly customized so the border highlights up my rage bar in time with my global cooldowns.
Flexbar2: The 4 buttons with Shield Block/Dev/Rev/SS are a flexbar2 button group that's been very slightly modified so it isn't actually clickable. They're just there so I can keep an eye my cooldowns and know which ability to use next.
Debuff Filter: The next four buttons below that are Debuff Filter setup to just show Demo/Tclap/Sunder/CS. If I don't see 4 icons there I know something's wrong.
Metahud, Debuff Filter, and Flexbar2 all disappear when I'm not in combat.
Here's my interface outside of combat:
http://www.ramenite.net/wowui2.jpg