My first team at 85 were 4 shadowpriests, but i found them a bit disappointing with damage. Often it seems like i didnt even get 10% off of someones healthbar. I was wearing tailoring pvp set and greens at that time though, so i assume they're depending a lot on good gear.
They're awesome on the defense though. With the fades, fearwards, shields, etc. But that isn't really shadow.

I switched to druids (feral cats for dps and resto for heals) which are both very nice. Personally i really didnt like the boomkins, but thats a viable option too.

My advice: go druids. They're so much fun.