Mana Drains/Burns
Now work of a percentage of your total mana pool.

Judgement of Wisdom
Now restores 2% base mana per proc instead of 1% max mana.
No info on proc rate/cooldown yet.

Torment the Weak
Is now triggered by attack speed slowing as well. It also affects Arcane Blast now.
It should be up all the time on bosses now without casting Slow because the tank has an attack speed slow.

Arcane Overhaul
Arcane Blast debuff is now a buff and lasts 10s. It's stacked by chaining Arcane Blast and removed when casting any other Arcane spell.
It increases damage of your next Arcane spell by 15% and cost of Arcane Blast by 200%. Arcane Missiles get the damage increase for all 5 volleys.
A new glyph increases the damage bonus of the Arcane Blast buff by 5% per stack, up to 15% at 3 stacks.
Arcane Blast is now affected by Torment the Weak as well.

Arcane Playstyles
Early simulations gave the following recommendations:
AB-ABar is your normal DPM cycle.
It might change to AB2/3-ABar when you get haste capped at 33%.
AB*3-ABar is your DPS cycle.
AB spam is your burn cycle, however with a bad mana conversion.
Use MBAM as soon as it procs. Use Molten Armour.

Spec Performance
Without the glyph, it's about 4% behind Fire/Frostfire specs, with more mobility.
Fire with Torment and Frostfire as usual are now neck-to-neck.
Evocation
Cooldown down to 4 minutes, 2 minutes talented with 2/2 Arcane Flows.

Elemental Precision
Is now 3% hit to all spells. No more double-dipping for Frostfire.

Dispel Resistance
Talents now only affect the dispel resistance of buffs and DoTs.
Winter's Chill and Polymorph are not protected by Arcane Subtlety anymore.

Procs items
Many items that procced on spell cast were changed to proc only on damage/healing spells.

Pyromaniac - 10% spirit regen instead of mana cost reduction per point.
Improved Blizzard - down to 20%/40%/50% slowing.
Arcane Flows - added -1/-2 minutes on Evocation.
Slowfall - castable on others now.
Blast Wave - Minor Glyph for -15% mana, no knockback.
Glyph of Arcane Blast - +5% damage on the Arcane Blast buff. Unknown whether it stacks to 15% with 3 stacks.
Illustration of the Dragon Soul - down to 20 SP per stack. About 10% better than Sundial/Embrace now.