Glad you asked!
For a healer, I can see a few different builds. Grace has been nerfed significantly, to the point that I can no longer see the 45/26 build I was looking at initially. So this is what I can see.
HEAVY DISCIPLINE
http://thottbot.com/priest/t#EIYpQq9kKd/KgNc
This build is focused on pre-emptive healing, with several raid/individual buffs for variety. Penance allows for rapid stacking of Grace in addition to its healing function. I chose to skimp on Mental Agility, something I rarely do, because the alternative was to not fill out Improved Healing, which was unacceptable. There are numerous talents I would *like*-- namely, Renewed Hope and Aspiration-- that there just aren't points for, which is too bad. I couldn't even think about adding Reflective Shield, which is a crying shame, too. Additionally, I chose Healing Focus over Holy Spec. Healing is too important to suffer spell interruption, especially for a build that relies on a channeled spell for its heavy-duty work.
Between powerful Shields, Divine Aegis, and Grace, this build can add a powerful dimension to tank-healing, but I see it as weaker for raid healing. It lacks raid-healing ability. Sure, it can heal individuals very well (for example, this build would trivialize, say, Dark Barrage so long as he's looking for it). But if you're this guy, you're healing individuals, not the raid. Additionally, you can't really bring more than one Disc priest. The build lives and dies by the Weakened Soul debuff, so there's no capacity for duplication. The first Disc priest is terrific; the second is MUCH less effective.
COOKIE-CUTTER REDUX
http://thottbot.com/priest/t#EIQFw2/ehNeIQh.
This build is remarkably similar to the build I have now. I use lots of Flash Heals with this build, but add CoH to my ******** Power comes from Spiritual Guidance, Spiritual Healing, and Empowered Healing; endurance comes from Serendipity and Imp. Holy Conc. I bring Imp. DS for its undeniable virtues and retain Mental Agility for CoH and Renew.
There are a bunch of small variations I could make here. I could pick up Surge of Light, but I'm not happy with the talent. For one thing, it actually *lowers* your heals/second. The instant Flash still invokes GCD, so is (long term) no faster than a normal cast, while being incapable of a crit. Still, instant is instant. I am curious to know how Serendipity interacts with SoL, though.
Another variation would drop Holy Reach for another point in Holy Spec and another in Lolwell or Test of Faith. Test of Faith is hardly my favorite talent in the tree.
HEAVY HOLY
Either http://thottbot.com/priest/t#EIM1/uhNcISh.P
...or http://thottbot.com/priest/t#EIM1/ehNeIQh.T
Both builds take the bare minimum of Discipline talents required to be effective and dump the rest in Holy. It's more worthwhile to discuss what I skipped than what I took:
--Healing Prayers. In raiding, Prayer of Healing is very difficult to use. With CoH in our ******** PoH is obsolete. So Healing Prayers affects only PoM and, while I love PoM and frequently keep it on cooldown, it's not worth two talent points. A possible third variation, though, would be to drop Test of Faith for Healing Prayers and maybe Lolwell.
--Lolwell. The new Lightwell is MUCH enhanced from previous incarnations. However, I still hesitate to use it. The fundamental problem with Lightwell was never the charges, or the amount, or the cooldown, or the breaking on damage; those were all gravy. The fundamental problem with Lightwell was, and remains, that it requires other people to take responsibility for their own health. Other people suck at this. It's not that other people suck; it's just not their job. It's our job. We're good at it, they're not. Thus, Lightwell just doesn't work. Sure, there are situations it might be nice, but I want a new healing spell I'll actually use. Still, with all these talent points flying around, I might try it.
The first variation I posted takes the max number of crit-oriented talents and Surge of Light to crank out the instant Flashes. The second just heals really, really well. Both are worth contemplation.
ACCESSORIES
Heavy Disc builds favor intellect over spirit, both due to Mental Strength and the additional smidgen of crit, not to mention the lack of Spiritual Guidance. That build would favor intellect, crit, and spellpower as its primary stats, with the occassional spellpower/spirit gem for blue sockets. For Glyphs, Glyph of Shield is a no-brainer. I might go with Prayer of Healing too, since the build is otherwise weak in area healing; Dispel is always nice and Flash Heal worth consideration.
The CCR build favors spirit and spellpower as its primaries, with yellow sockets satisfied with spellpower/int or SP/crit (if SoL is in the build). For Glyphs, CoH and Flash gain favor, with either Renew or Dispel filling out the array.
Glyph of Spirit of Redemption is worth consideration, since it has the potential to be a major save-the-day item. The question, of course, is: Is it worth losing reliable performance for a chance to salvage a disaster? The answer, to my mind, is no. In many situations, if the priest dies, the wipe is well advanced already. Prevention of a wipe through constant good output is preferable to trying to rescue a wipe. Let's face it, the only reason we take SoR *now* is for the 5% spirit buff! Without it, I'd probably pass on SoR.
Glyph of Lolwell is useless. Glyph of Holy Nova should be better than it is, since we have real AoE in WotLK, but it's still a limited spell. Why would I run up into the mess, risking a break of crowd control, and cast Holy Nova as a healing spell when I could stand back safely and use CoH instead? Especially since CoH is smarter and raid-wide, whereas Holy Nova is group-limited? Answer: When I'm using Holy Nova as a damage spell. In that case, the Glyph is useless.
Glyph of Fear Ward? In a raiding context, not very useful, especially with Berserker Rage now available in Defensive Stance and shaman available to both sides.
So! That's my assessment of priest builds in WotLK. I'm sure in a few months I'll look back and bemoan how foolish it all was, because that happens every time, but for now that's all I've got. Any questions?