From GC:
Desperate Prayer is a pretty different ability. They really only have the name in common. In Cataclysm, Desperate Prayer has a 45 sec cooldown (down from 2 min). The lower cooldown will let you use it often as leveling.
Holy also has a talent that when you use Desperate Prayer (to heal yourself), it also heals the most injured ally (a portion of the healing done to you), turning it into an instant, smart Binding Heal.
Sounds really really interesting. The spell is still to expensive, but could be a good thing now that Surge of Light heal part has been removed. I always think that instant Binding Heal would be awesome for PvP. Finally the time has come!