Fire spec slows you down since you'll have to keep running away from literally everything you attack. Frost is used for survival just because you can efficiently run away from mobs instead of being a glass cannon.
http://realmplayers.com/Talents.aspx#obhA0oZZVAGcofthoIF YOU REALLY DO NOT CARE ABOUT AOE'ING SHIT...
Arcane Subtlety + Elemental Precision: Vanilla Spell Penetration. Frost spells are binary; you either resist/miss or hit. There's no partial resist so you want to increase your chances of hitting rather than not.
Also, I had spirit stacked gear throughout my leveling just to regen mana faster when I drink. It saves you time if you have spirit+int gear and want to continue the grind faster. It's also a life saver when you need to conjure fuckloads of food/water for needy bastards inside cities.