I just revamped my UI this week based on power auras classic. I lifted the most of the auras Beru described here (though I modified them to fit my needs):

http://fallingleavesandwings.wordpress.com/2011/01/03/berus-resto-and-balance-druid-power-aura-exports-cataclysm-update/

Power auras creates all of the icons to the left of my character (they pop up when the spells are usable, disappear when they're not), and the big icons pop up in the middle as notifications telling me important things I need to do (in this example, clearcasting is up - you can see the seconds ticking down in the middle of the icon). It's nice to have something big and obvious like this when you're also trying to focus on health bars. Here is a quick screen shot of the HUD I settled on:

http://i53.tinypic.com/muc3f8.jpg

I use tons of Mouseover macros, XPerl Unitframes (I use Big Buffs to see my HoTs clearly), and I configured my Gnosis to display buff timers for Rejuv and Lifebloom when I mouse over a target (so I can check my hots on raid frames w/o targetting people).

I'm also a raid lead, which means I also need to keep a ton of other information at my fingertips, so my UI is pretty complicated. If I was only concerned with healing, I could probably simplify it a fair bit:

http://www.youtube.com/watch?v=7wsWXeYHgF0&feature=relmfu