Updated now patch day is here:

Raid specs for Ulduar

In order of DPS:
FFB/Focus*
TTW/FB - 20/51/0, 18/53/0, 19/52/0
Arcane
FFB
Frost/TTW

*FFB/Focus means you use some 11+ Arcane as second spec, cast Focus Magic on someone (Frostfire/Fire Mage or Moonkin/Shadow Priest as 2nd choice), and then spec back to FFB (0/53/18 or similar) whilst in the same raid. It's not clear whether Blizz will jump on this and fix it so you can't do it. Either way, its a hastle to do given you have to redo on death, so up to you whether you want to try it. EDIT (21/4): Yup Blizz noticed and have just "fixed" it, so FFB/Focus no longer good option.

The first 3 specs are very close in dps, and are going to depend on gear as to which is best for each individual. Also, TTW/FB apparently has threat issues in Ulduar, and Arcane has mana issues in the longer Ulduar fights.

General talent notes

1) Spirit now affects crit - with Molten Armor up, 35% of your spirit is translated into crit rating. As a rough indication, at level 80, 45.91 crit rating = 1% crit.

2) Glyph of Molten Armor gives a further 20% of spirit translated into crit (i.e. in total with above, 55%). With both up for example, 600 spirit (assuming raid buffs) would give 330 crit rating, and thus 7.18% crit.

3) Improved Scorch now only gives 5% crit to the raid, down from 10%. However the talent now gives a permanent 3% crit boost to fireball/scorch/frostfirebolt.

4) Winters Chill also gives 5% crit, but only grants the 3% permanent crit bonus to frostbolt. Winters Chill DOES now stack with Improved Scorch, or did last week - whether this will be the case on release, have to see.

5) Warlocks will get a talent in the patch (improved shadowbolt) which will enable them to provide a 5% crit buff to the raid. However, it is looking like most locks are unlikely to take this talent so Fire and Frostfire mages should still take improved scorch (especially because of the 3% permanent crit).

6) Glyphs: For TTW/Fire and FFB - Living Bomb, FB/FFB, Molten Armour. For Arcane - ABlast, AMissiles and Molten are likely the choice for Arcane. Last sounds slightly bizarre so worth experimenting.

TTW/FB spec

1) This is very hit dependant - you need to max or come very close to maxing your hit (17%):

446 hit - no buffs - 17%
420 hit - with a draenei in your group (1% hit aura) - 16%
368 hit - with no draenei but either a shadowpriest or a moonkin in the raid - 14%
342 hit - with draenei in your group AND shadowpriest/moonkin in the raid - 13%

To play it safe, given you can't guarantee in Laz that you will get a draenei in your group, but most of the time there will be a shadowpriest raiding, you could get away with 368 hit.

2) Gear for Hit (until cap) > spell power > haste > crit

Amount of crit needed is unclear - something between 25-30% fire unbuffed is probably ok, but I've seen people with good dps on just over 20% unbuffed, although they had well over 350 haste. EDIT: Does appear that you can get v.good dps with just over 20% unbuffed crit BUT only if you also have around 400 haste, are hit capped, and have 1800+ sp. In short, lots of haste is important for this spec.

3) You will need upwards of 1900 spellpower unbuffed to really make this work on a par with arcane.

4) Glyphs for this spec after 3.1 should be Living Bomb, Fireball, and Molten Armor.

5) In terms of talents, do take World In Flames - don't take Dragon's Breath or Blastwave, as AOE is less of a factor in Ulduar apparently (get ready to go back to sheeping... or rabbiting). Other talents to play around with are combustion (tending now to get dropped), Student of the Mind versus arcane meditation, and flame throwing (i.e. going for 20/51).

6) This is a raiding spec - do not expect to do wonderful dps in heroics with this

7) Some variants:
http://www.wowhead.com/?talent#of0Vck0fZ0EcoRhIhVhbhct
http://www.wowhead.com/?talent#of0Vcu0cZ0EcoRhIhVhbhct
http://www.worldofwarcraft.com/info/cla ... 0000000000

Arcane

The previous usual spec of 57/3/11 is still the general one for Ulduar - see Billy's post for more detail on it, what you need, and how to use it. Main difference is the switch from Mage Armor glyph to Molten Armor.

Professions
Best mage professions now are tailoring (due to new patch stuff) and jewelcrafting. Tailoring though takes an age to level up and this may well change in the NEXT patch, so up to you.

Other Stuff

We get a big bouncing PolyRabbit.

Mirror image will no longer polymorph thankfully, but now triggers a regular global cooldown

Glyph of improved scorch now applies 5 stacks not 3, but unless one mage wishes to sacrifice themselves for the good of the raid, you will lose some dps taking this as opposed to living bomb.