I started playing my spriest at the end of wrath.
It was my First lvl 80 back then, the First and only One I've been raiding with in wrath.
When we came to cata, i lvled the priest First and did raiding with it. At some Time, i also lvled a prot pally. Tried raiding with it too, but didn't work out well.
Later on in cata (been raiding all exp with that shadow) in DS i started raiding with my newly lvled Hunter. I was playing with a f&f guild, where we had some really, really Bad peeps, but with my help, they managed 5/8hc in DS, since I've been knowing what to Do for months already. It was really fun to play the Hunter, but as i was still weaker than my shadow, i stopped raiding with the Hunter.
Also in DS Content, before MoP came out, i was 2 pieces and the legendary staff away from Full BiS gear, what Made me really feel awesome.
Then harder times were coming... In MoP, my raid group got disbanded, and i had little Chance to get into the 5.0 raids until 2 weeks before 5.2. Yep, i got carried for some gear to be able to Do ToT. Since i could Not raid, i lvled a Monk to 90. I was about to Main it, but it was broken, and i suck at playing a melee dps. So i sticked to my shadow, that I've been now playing for 3 years already.
In ToT, my raid group, really, really sucked, we couldn't even get past horridon on normal mode! I then looked for a new group, found One after gathering an ilvl of over 500. When the raidlead left us over night, our Main tank took over the lead and we kept on raiding as a group. Since i was Not satisfied (i guess i spelled that wrong) with our progress, i switched to a new guild after clearing SoO normal, since we could Not get immerseus HC down.
Even tho my new guild struggled with a guild Fusion, which Fell apart after 3 months and thus losing 3 months of progression, we managed. To clear SoO HC eventually.
I still love playing my Monk tank tho in normal mode, even tho i'm pugging with it.
Wall of Text =P. In short, i sticked to my shadow priest because i had a lot of ups and downs with it, because it was my First Max lvl char in 3 expansions and because i like the gameplay of a mind-threatening freak xD