I started my Priest (from a Resto/Boom Druid) late into ICC to help my 10/25man raid get Lich King, as we didn't have a single raiding Priest at the time.
And while I have benched her a time or two to raid as another class (Shaman at the start of Cata [ugh...], Druid tank for DS, and DK tank for early MoP), I always come back to her out of convenience (raid composition), because I miss playing her, or a mix of the two.
It's too early to tell what I will be playing next xpac, but I wouldn't hate it if it were my Priest.