Hey, i just read this on wowwiki, about changes to priests in Wotlk.
Circle of healing - Will now have a 6 second cooldown.
But it's not just bad news..
They've made it so that it Now works on any targets in the caster's raid, and is now a "smart" heal and chooses the lowest health targets to heal first within its range.
=) which is good. Other significant changes that you may know is that "Wand Specialization" (Discipline) has been removed
and replaced with a talent that gives u 1/2/3/4/5% more healing and damage =D which is so YeY!
However, bad news for a moroes fight :b
Shackle Undead now costs 9% of base mana
Argh! And Also, Psychic scream will coste 15% of ur base mana.
however this is awesome for Shadow pve priests -
Shadowform (Shadow): Now has an innate 30% threat reduction. Now has a shapeshift UI.
WOW! =) Well if u wanna read the other changes go to Wowwiki - it's all there .

And by the way, yes im not quitting when wotlk comes, i just have to try it ^^
Greets,
Ragg