I raid as Shadow and PVP as Discpline, and my UI here:
http://www.mmo-champion.com/index.php?topic=39094.0
works perfectly for me. When healing, I don't even use my action bars because I use Grid + Clique which lets me cast certain spells depending on how I click the players on Grid (left click = flash heal, right click = penance, alt + left click = dispel) etc. Yes at the start I was a little slow, but once you memorize everything it becomes instant results without having to think.
If you don't want to click on the link, here's a screenshot:
See it in action: (High definition)
http://www.youtube.com/watch?v=x-a3lK9s9ps