If you are going mainly for PvP Unbreakable Will is very handy. There was one other deep talent that I was curious about you not taking but it was probably a preference thing. The spec looks ok otherwise.

Holy Nova is kind of expensive, but very nice. If you are getting zerged Holy Nova times 5 is deadly because while it's prolonging your life it's damaging the melee chewing you up :/ One trouble with priests is that they don't really start getting good until around 40, regardless of spec. I like disc for leveling and BGs. When you hit 51 you can be a real asset with Penance and Pain Suppression on noobs trying to tank with a 2h'er, lol.

Do what's fun and just try it out. I suggest respeccing all, or all but one, to shadow at 40. Mind Flay is fun.