Shamefully stolen from the Mage boards (and I'm not even shadow >=D), but nevertheless an interesting quesiton. At what point did the priest class "click" for you? When did you do that awesome thing or obtained that ability that made you go "Hell yeah, I love the priest!"?
For me, it was a long time back. I decided to play a priest before the beta was even out, and at that point basically every spell I learned about the class interested me, be it Lesser Heal or Renew. I had another small 'click' several years later; I had a little paladin healing experience by then and was healing an instance on my druid when I noticed the lack of direct heals. It was then that I decided to go back to playing a priest because healing-wise, they have it all. Not solely HOTs like the druid and not solely direct heals like the Paladin, but a steady ********