XPerl and Clique. No question hands down the best thing that ever happened for my healer. Unfortunately as a holy priest I have button combos out the wazoo for all of our heals. But click healing is sooo much easier than target healing. Tho I know alot of pro healers rely on the "who is targeting my target" for when they heal.
XPerl is solid just because I love the deficit view of health numbers. The minimalist UI and other features are just gravy.
But at this point I would panick without both of these.