Main Problem with Shadow Priests in raids imho is the lack of epic itemization for this spec.
Look at the Prophecy (T1) and Trancendency (T2) Sets. They all have +healing insted of generic spellpower on them. This puts you in an awkward situation: since collecting the priest specific set items isn't worthwhile, you have to resort to collecting some generic not classbound spell power or shadow power gear. Unfortunatley these items are rather limited in supply and you have to compete with Mages and Warlocks for these. Though I've always dreamed of playing a shadow priests capable of raiding, I wouldn't want to spec back from holy now, because of all the +healing gear I have accumulated over time.
This is going to change with AQ drops though where you will find several items specifically tailored for shadow priests.
Regarding the talent discussion, I would sugguest to wait for patch 1.10 anyway when we get our big priest revamp ;)
Look at the Prophecy (T1) and Trancendency (T2) Sets. They all have +healing insted of generic spellpower on them. This puts you in an awkward situation: since collecting the priest specific set items isn't worthwhile, you have to resort to collecting some generic not classbound spell power or shadow power gear. Unfortunatley these items are rather limited in supply and you have to compete with Mages and Warlocks for these. Though I've always dreamed of playing a shadow priests capable of raiding, I wouldn't want to spec back from holy now, because of all the +healing gear I have accumulated over time.
This is going to change with AQ drops though where you will find several items specifically tailored for shadow priests.
Regarding the talent discussion, I would sugguest to wait for patch 1.10 anyway when we get our big priest revamp ;)