Overall, I'm definitely "meh" on the changes. Acts of Faith are now very likely to go off, but you only get one. This means that the Simalcrums are now required purchases for any squad that can take them.
Both Celestine and Uriah (the go-to characters in the WD 'dex) have been made slightly more expensive and had their abilities toned down. Both are still useful models to have, though. My counts-as Celestine will probably still be my Warlord all the time, if only for fluff reasons. That being said, my Cannonesses might get some time out of the box. Jacobs is no longer a WTFblob character. Both changes were straight-up reductions in the power of the characters.
I think Celestine's resurrection ability irritated too many gamers at GW. Now it's nearly guaranteed to go off... once, as it's an Act of Faith now.
Kyrniov is Sir Not AppearingInThisCode x. His mace got moved to the Relics list, though.
Good God-Emperor, the Priests. This just opened up all manner of awesome combos with Battle brother units. Dirt cheap, access to good toys and those rules! And the guys unlock fscking Battle Conclaves... and 5 per Sisters detachment? Forget the commissars, that 50-man IG blob just got a whole lot meaner! If I were running a melee Guard army, I'd bring an allied Detachment of Sisters just for these guys. And maybe a squad of Pentitent Engines for the lulz.
Celestians are still Celestians.
Repentia... at least they are slightly cheaper and can take transports now. Yay? The change to their Act of Faith makes them a liability when trying to kill any MCs (a Shield of Faith save is not a real save, IMHO). Neural Whips actually make some sense now, but the net effect is that the to-wound roll is still crap against MEQs, let alone Necrons. This squad can't take the Simalcrium.
The HS slots are the same as before: Everything that is not an Exorcist has the crippling disadvantage of not being an Exorcist. The Pentitent Engines are slightly cheaper and the randomness in their attacks has been removed. Act of Faith changes burned Retributors, they NEED a Silmacrium Imperialis unless you're using multimeltas for some reason.
Seraphim are another squad that can't take the Imperialis and such were hurt by the Act of Faith changes. At least the hand flamers are cheaper now.
Immolators are now pretty much crappy Razorbacks, with their only redeeming feature being the TL multimelta availability. They're slightly cheaper than the previous 'dex. I don't have my SM codex on hand to compare to Razorbacks.
Rhinos are still Rhinos. Shield of Faith does give that Hail Mary save.
I don't think the Command Squad is worth taking still, although the relic banner is pretty neat if you're running a CC-oriented army (or a friendly allied army).
But really, priests are like mini-SM chaplains with better weapon options and a awesome special rule!
Remember that Condemnor Boltgun that nobody used? It's still here. It does explicitly affect Psychic Pilot, so that's nice. Doesn't even need a wound to get though so far as I can tell. Cheaper, too, and all sgts can take them if you want to feel silly.