I was a bit bored at work today, and did some calculations...
With the new talents a naked priest with 41 points in shadow form using SWP, Vampiric Touch (+mana currently isnt limited to group), Vampiric Embrace, and Mind Flay would be capable of at level 60:
318dps, 95hps, restoring 16 mps, providing +15% bonus to shadow damage, and +5% bonus to all spell damage, averaging about 4 damage per mana.  

The down side would be not being able to heal due to shadow form, so without using that:
285dps, 85hps, restoring 14 mps, providing +15% bonus to shadow damage, and +5% bonus to all spell damage, and still able to spot heal.

Notes: 
+damage from gear only makes the numbers go up.  + damage from gear: SWP - 100% Mind Flay - 50%, and Vampiric Touch - 100% (at the moment in beta) bonuses added Before %damage increases from talents.

Questions about multiples:
Does Shadow Weaving stack 5 times total per mob, or per priest?
Does Misery stack one time total per mob, or per priest?

Comments:
If you take two decently geared (about +140 damage) shadow priests  on a raid or any group, you're looking at (assuming that the answer to my questions are no, between the 2 priests) 700dps, 210hps, and 35mps.
35mps = 175 mana per 5 seconds


This is a bit crazy, and seems like it would be extremely valuable to a raid.

What's your take?