EDIT: My original calcs were wrong.  There isn't a secret nerf.  It is equal or better!
The following includes trying to get at all the mana regen or saving abilities. These may not be valid templates in themselves, just what is POSSIBLE.

I don't want to be all negative, there are some wonderful new talents and improvements to our spells ingeneral that I really really appriciate. There were just some things I noticed, and I wanted to try and get them into hard numbers to look at.

I wish I was better at number crunching...this could be all wrong. Please feel free to correct me where needed.

After playing around more with the talent calculater, I'm starting to feel a little nerfed, at least looking at this strictly from a RAID priest point of view. I realize Blizz probably thinks we shouldn't have ginormous mana pools AND superior regen...but: As it is now, I can get Mental Str, Mental agi and meditation from Disc AND still get Spiritual healing, Imp Healing and Imp PoH. Let's set up a raid scenario...using 5 minutes as our base time for casting without any real break (SLACK is non-stop dang near, but just for this test, we'll use 5 minutes). For an average lvl 60 good blue/some epic geared priest, this currently means:

- Mental Str: 700+ mana base pool.

- Mental Agi: Saving of 10% on PW:S and Renew. I will estimate that a raid priest casts renew 2 or 3 times a minute average (?), for a saving of around 90 mana a minute here. PW:S is more sporadic, sometimes not being used for long periods, sometimes spamming it on a person or self (SHazz and the Baron anyone?), so it's hard to estimate this in. So say 450 mana saved in our 5 minute span.

- Meditation: 15% (or around 38 to 45 points of spirit, assuming we have between 250 and 300 spi) to continue regening while casting. Someone correct me here...but I think that calculates into 5 to 8 mana per tick, right? I think this comes out to be 500-800 mana in 5 minutes.

- Spiritual Healing: +10% to all healing spells. I understand this does not scale with +to healing gear, but works on base amount of the spell. So average Flash is +90-100 healed, Gheah is +200-250 healed. Not sure how/if it applies to renew. Let's assume 3 flash heals and 1 GH and per minute. That's up to 2500 extra hp healed, which equals about 1GH, so say about 800 mana saved in 5 minutes. (I left out PoH intentionally here, as it depends on how many people you heal and such, and I want to compare current talents with upcomming talents, I'll just leave it out of + to healing there as well, it'll equal out. Boy, this is so unrefined, bear with me here)

- Imp healing and Imp PoH: Totally vary on how often you use these spells. But it saves about 90 mana on Gheal, and 110 on PoH (I think...doing this part from memory). If we pretend 1 GH and 1 PoH per minute, this saves 1000 mana per 5 minutes.

So, we have 700+ more mana to start with, and we are saving or regening a total of 3100-3450 mana every 5 minutes!  Add the 700+ base, and that is a total of 3450 mana to 3750 mana!

The NEW talents will allow us to pick a few different combo's of mana saving/regen abilities. Here is one trying for mostly Holy (healing), with as much as we can get out of Disc (regen):

Imp healing, Imp PoH, Spiritual Guidance (new) and Spiritual Healing, Meditation and 4/5 of Mental Agi.

- Spiritual Guidance: (25% of spirit added to dmg and healing) Again using 250-300 Spirit, this gives us 62-75 +healing (and +dmg also, very nice add there). Will this be applied 100% directly or the same way all current + healing gear is, we will have to test. Let's give it the benefit of the doubt and and give it the full 100% to all healing spells (wouldn't that be spiffy?) So assuming the same scenerio as before, that is 3 Renews, 3 flash heals, 1 GH and (no PoH for this Calc either). Even including the renew at 100%, that comes to 2170-2625 extra points healed. That equals about 1 GH,. Say 800 mana saved over 5 minutes.

Using the figures above for the rest of the talents, and reduce Mental agi from 10% to 8% (360 instead of 450), this totals 3460 to 3760 mana. I updated this number. It isn't that different.  My initial calclulations were WRONG.

Ok, let's try the other way around. This is all we can get out of Disc, with as much as we can then get out of holy:

Meditation, Mental Agi, Mental Str, Divine Spirit (moved way up tree, reduced to 17 points, may get higher with training??), Imp Healing, Imp PoH, 2 points in Spiritual guidance.

-Divine spirit: at 17 spirit gives us about 2.5 mana per tick, so 250 mana every 5 minutes.

-Spiritual Guidance at 10%: +25-30 healing. that is 875 to 1050 extra points healed, or...about 1 flashheal. Say 350 mana in 5 minutes.

Again using the numbers we have already established,we again have our 700+ mana base, and we are regening or saving 2550 mana to 2850 mana, add the 700+ mana and that is 3250 to 3550 mana. only about 300 mana difference

I realize that some of our spells are being inherintly improved (casting times lowered, innner fire and PW:S improved), and that there are some skills and abilities in these trees that will help our survivability. (New Spirit of redemption is very promising if it allows us to cast more than one heal in those 10 seconds. Lightwell could be great, depends on what kind of dmg breaks it and such, we'll have to test it). Not sure about Spellwarding (would this help in high end instances?) or the new Holy nova either, all these things will be tested I'm sure.
ok, I must correct myself at this point.  The new talents are about the same mana-wise. With the other talent options...it IS an improvement.  I oppologize for the nerf comment, I was wrong.  All the same:

In summary, can I have about 10 more talent points please? And some new Spirit armor??  lol