@thesmuggler: Go haste, or an evil Akraen will show up and eat your face clean off. On a more serious note: Akraen is VERY convinced of going haste, and I do see the reasoning behind it. Someone, I think it was Nathyiel, also demonstrated quite nicely why haste scales with more of our spells then mastery. Personally, I found it to be the better playing experience as well.
The only thing to keep in mind that sims (and to some extent my personal experience) have shown mastery to be better for straight single-target situations (or by extension pure two-target cleave). Now, I don't need to tell anyone that sims are problematic, but for straight single-target I still find them to be worthy of consideration. Since that is a rare situation anyway, and 2pc-T16 also favours haste, I'd say go for haste.
@Akraen, or anyone really: There's been some talk of Frost Bomb around here, and I haven't really kept up so far. Is it really feasible to play with it now? If yes, in which situations do you use it? I get the more predictable FFB-generation, and that seems wonderful with the 2pc, but is it really overall more FFBs? What about the mobility issues? Seems still a bit akward to me.
@pete: I feel your pain, I just recently went over to Arcane as well. The issue obviously is on a conceptual side. If I am geared completely for Frost, say in full haste, I will deal X amount of dmg with a bomb. If, without any other changes, I know switch over to Arcane, I will deal the same X damage + anything I can get out of my mastery. Frost just falls radically behind there, and there is nothing they can really do to change that (except nerf arcane). I do love Frost, and I obviously repeatedly argued that it is a valid specc (which it is), but it does feel frustrating to see that it is completely lacking a defined strength, or a fight to shine really.