Long time player here, healed on my Pally for all of Vanilla content, Holy Priest for BC, and did a bit of both of them (including Shaman) in Wrath, however only really progressed as my Holy Pally.
I have been trying out my recently leveled Druid, Holy Pally, and Resto Shaman a lot in raids and heroics to try and get a feel for the new healing mechanics. I have not been following the forums too much in the past month, but have been keeping up with mmo-champion.
Overall, I'm asking how Disc Priests (in PvE) will compare to other healers once at level 85. Obviously Cata is not out yet, and everything is still subject to change, but I'm trying to get a general feel of things. I'm not liking my other 3 healers too much since the patch, but enjoyed what little PvE content I did on my Priest throughout Wrath.