The new Improved Soul Fire tooltip says it just provides a flat 15% haste buff after using Soul Fire. There's no requirement that it be used with the target at +80% health like before.

This seems like a major, major buff to destro pvp to me. Less so the other specs since they have to give up Demonic Rebirth to take the talents in destro (will they do so?) plus Soul Fire hits harder for destro than affliction.

I admit I find destro pvp a lot more fun than affliction pvp and I've been a bit disappointed by the Cata beta arena reports that have afflictions steady and reliable damage outpacing destro's burst. So destro could use some buffs and it looks like this is a very nice one.