Penance's main benefit seems to be that (if it works like Arcane Missiles) it would apply 3/3 Grace in one spell, taking only 3 seconds to do so.
My main problem with the tree is that is still feels very much like a PvP healer tree overall, and is very, very gimmicky for PvE. It has a billion tricks, but just from looking at it all I can tell is that it is very crit-dependent. As such, it will probably be sharing much of it's gear choices with Destro or Demo warlocks and most Mages. It also makes it difficult to build a dedicated PvE setup overall. At the moment, I'm looking at 53/18/0 for PvE healing, most notable talents in Holy being Improved Healing and Inspiration (the latter being a giant DUH for a crit-focused tree). Link below:
Yarr! Tools :: Priest 8472
Yes, I skipped Silent Resolve. This is from a more-or-less pure raider POV, though, and when is the last time you had problems with healing aggro in anything over a 5-man? I also wanted to take the other 2 points of Aegis, but could not do so while maintaining 3/3 Improved Healing. If mana turns out to not be a problem, then I'll drop it in half a heartbeat to finish out Aegis and the last point of Reflective Shield.
I'm no PvP buff, but if someone could go through and take a look at that, it would be appreciated. I see a LOT of potential there. I'll probably edit in my build later, but I'm willing to bet that even my first build shows my distinct lack of end-game Priest experience.