Arcane Blast
The mana cost ramps us like this; 190 / 265 / 340 / 415 Cast time: 2.5 / 2.1 / 1.8 / 1.5 It’s not every mages favorite spell, but has its uses. You can burn down your remaining mana on a low health raid boss or mix it into your regular cast routine (letting it wear off before recasting.) It’s a pretty efficient spell without the stacking, and very high damage with the stacking.
Invisibility
Well, it took some time for Blizzard to add invisibility back into the mages arsenal. It’s different from the way it was way back when though; The spell is instant, and the 8 second fade happens without channeling. During the fade period, you can cast non hostile spells without breaking it (Blink, evocate, teleport, hearth). Any hostile action (including dots on you) while fading or invisible will break the effect. Once the 8 second fade is over and you actually become invisible, doing anything beside moving will make you visible again. Turning invisible drops all threat on any mobs you have built up, which can be useful on certain raid fights.
Spellsteal
The spell that is to be stolen is picked randomly from whatever magical effects the target has available, regardless of the order they were casting in by the target. The advantages in PvP range from large to nothing. You might steal Fel Armor from a warlock, but you could also end up with the remaining last second of the trinket effect he had active. Whether to use this or not depends on your target, and what you end up stealing depends a lot on luck. It has its uses in PvE as well, where you can take the time to use detect magic to figure out whether a certain mob has something worth stealing. After a while, you will know which mobs have the useful buffs and use Spellsteal at the right moments.
Molten Armor
This one is situational, as most of the new spells are. The Impact talent works nicely with Molten Armor though, and the extra spell crit does not come unappreciated.
Ice Lance
All I can say is.. Frost Nova plus Ice Lance turns things into meaty icecubes. Great PvP spell, and its mana efficient too.