My priest was level 30 all of Wrath, but spamming Renew is NOT viable in Cata, so I'm still a little confused why people are. Having Renew on like 5 targets at a time is awesome, just like a Rejuv, but it's nothing like PoH in play-style or application.
PoH Heals 5 people and applies HoTs and factoring GCDs heals way smarter than Renew.