The full list of changes is after the break, but here's a quick summary: Evocation cooldown reduced to four minutes, with Arcane Flows also reducing the cooldown even further. Arcane Blast got an overhaul -- will now increase the damage of your next Arcane spell by 30%, or you can stack it, for a higher mana charge. So you can use it to buff Barrage, or use it as it is now, just upping the Blast and mana costs every time. Interesting.
Elemental Precision lost the Elemental and will work on all spells, and Improved Blizzard got a slight nerf, with the snaring effect percentage reduced. Actually, that's most of the changes right there, but for those of you at work unable to see the forums, they're pasted after the break anyway. I don't play a Mage but it looks like you guys got off easy -- Arcane is the real winners, but even Frost and Fire got that Precision buff.
Update: GC explains the Blast change better than I can.
1) Evocation – cooldown reduced to 4 min.
2) Arcane Flows – now also reduces the cooldown of Evocation by an additional 1 / 2 min.
3) Arcane Blast – overhauled. Will now increase the damage of your next Arcane spell by 30%. However using Arcane Blast itself does not consume the charge, but instead increases the mana of your next Arcane Blast, up to a maximum of 3 stacks. You can alternate Blast and Barrage to keep buffing Barrage, or you can build Blast up higher for a heavy mana cost.
4) Torment the Weak – now works with Arcane Blast and does bonus damage to targets afflicted by any kind of slowing effect (e.g. Thunder Clap).
5) Elemental Precision – renamed Precision and now works on all spells.
6) Improved Blizzard – snaring effect reduced to 20/40/50%