Looks like there are some big changes in store for priests on the patch 5.2 PTR. Blizzard released a PTR patch note preview late last week and I'm honestly a bit baffled by some of the changes. Keep in mind, I am not often baffled.
The biggest change is that Power Word: Solace is being redesigned. The talent will now replace Holy Fire in the player's spellbook, but interact with other priest spells and abilities just as Holy Fire does. The new version of Power Word: Solace will be instant cast, cost no mana, and restore 1% of your maximum mana on cast. Surprisingly, the patch note preview makes no mention of redesigning Shadow Word: Insanity, the shadow portion of the talent.
Now it's no shock that Blizzard decided to redesign this talent. A quick glance at WoW Popular will tell you that almost no priests are taking it (in fact, it looks like more of us are taking Dominate Mind than Power Word: Solace). Shadow priests certainly aren't taking the talent, and most healers will tell you it returns too little mana per cast to be worth it.