I switched to arcane from frost a few days ago, so I have some recent experience with this.
I'm not sure how viable it'll be to switch between the two from boss to boss. The biggest difference is that frost wants haste to 14,242 rating and then mastery (or full haste, if you go that route; see Akraen's guide for details), where arcane only wants ~9450 haste before going full mastery.
If you get frost's 14242 haste rating, that's a whole lot of mastery your arcane spec won't have. Since mastery is great for arcane and good for frost, and frost will lose less from mastery than arcane wil
