I've been trying to find out as much as I can about how mind spike is going to work come Cata, and I really can't find much. I see that it now removes all Shadow DoT's and increases the crit chance of mind blast for 30 seconds. Will we just stack this every time the duration ticks off or is this going to be a useless ability in Cata?

Someone having access to the beta knows if the SW:P rolling haste is fixed or if they plan to fix it? It's obviously not "working as intented" and they already fixed this issue in the past (leaving the rolling crit that is now fixed but the rolling haste reappeared), but it seems to be still broken on live even with 4.0.3 release.
So i wonder if being a troll will be mandatory for cataclysm's shadow priests, as 20% haste on SW:P is so much of a dps increase.

If in a 10man raid comp with a holy pally and resto shaman which priest healing spec seems to have the best synergy with those two classes in cata? Or can that really even be answered at this point?

I'd say the best synergy is with Disc just because it brings absorbs that you can't get anywhere else, and penance is nice too. Although if your group is any good either spec should be fine, at this point in the game with decent gear the three of you could just take turns aoe spamming the raid.

So since Mind Flay obviously work like DoTs do now and can't be clipped with another Mind Flay, how do you manage to clip your Mind Flays with Mind Blasts/VT/DP? Due to delay and channeling like 4 mind flay will put the "tick" things on Quartz behind it seems to be very hard to actually clip Mind Flay properly nowadays. I mostly try to avoid trying to clip it and just wait for its whole duration. Is that still a DPS loss? Is there any addon that actually keeps track of the "refreshes"?

First off, most Spriests will recommend switching your cast bar to "gnosis". It is a superior castbar add-on.

The spell queue mechanic doesn't work the same way for channeled spells/dots as it does for cast-time nukes. I have found myself still to clip MF when needed. Are you trying to clip MF on purpose? because for anything other than VT re-cast, there really isn't a reason to clip it.

How is Gnosis superior to Quartz? When I mean clip I mean stop channeling right after a tick. Isn't the Mind Flay cast different now? I thought it refreshed the current Mind Flay

In terms of Veiled Shadows versus Mental Agility, does MA still come out ahead for a mixed PoH healing priest? Obviously it is far superior for Renew raid healing, and VS is perhaps better for tank heals (since Renew is refreshed by Heal Chakra, so it should be only PoM and HW: Serenity). Basically, is Renew blanketing what makes MA come out ahead or is VS a talent that just looks better conceptually?

Well Mental Agility also affects Prayer of Mending and Circle of Healing, both of which are relevant. Realistically though, only level 85 matters. You have to spend 32 points in Holy, so the question is where to spend your other 9 points. You aren't spending more than 5 points in Shadow, so you are guaranteed to spend 4 in Discipline. The better comparison is between second tier discipline talents and first tier shadow talents.

I can't say for sure without seeing the encounters, but if they are anything like the past raids, the value of 6% extra run speed will trump all other considerations. So that means Mental Agility is the better choice because it unlocks the second tier of discipline.

With some really fuzzy napkin math, I'm pretty sure that MA is just flat better in terms of MP5, plus it has the benefit of being always active. It's possibly still better even for a tank healer hitting PoM on CD, but my math was very, very fuzzy and using current mana pool and spell cost values. In theory VS is going to scale better, but I don't know what the threshold is.

Possibly going to just switch between Darkness and Inner Sanctum per fight (16% > 10%, but still situational with all the speed boosts we have, and the AoE boosts other classes bring as well).

It doesn't any more, but it reduces the spell damage taken, which is not outstanding (especially for early tiers, where there is traditionally less raid damage), but always nice. But I agree on your point: for fight where it is useful (which also, traditionally, includes between 20% and 50% of the fights of any tier), the increase in movement speed really outperforms the other option.

Assuming this, we have 9 points for both discipline and holy trees:
- 8 at least will be in disc, including 5 in MA + Twin Disciplines, and 3 in Inner Sanctum
- the 8th point can be either 3/3 MA or 3/3 Twin Disciplines
- the 9th point can be either 3/3 MA, 3/3 Twin Disciplines, 1/2 Veiled Shadows or 1/3 Darkness.

Evangelism without Archangel makes little sense, and Soul warding at 1/2 is not sufficient to remove the CD, so I'm not convinced about it. THere is few difference between a 3s CD and a 2s CD : you can't spam it, but you can use it once every two spells.

I really think that 1% haste is currently the worst option. 1% haste for one talent points seems weak with the new reduced trees.
It compares unfavorably with Twin Disciplines (2% healing is in most cases better than 1% haste, unless healing is really really about frantic reactions to focused deadly incoming damage).
And as long as we are mana constrained, mana regeneration is usually better than haste.