It's awesome. Super useful in close quarters house fights. I just get ambushed down in the chapel and stand in front of my opponents in a doorway, my companions behind me. I cast Thunderwave and then use bonus flight to hover over the heads of my comrades behind them.
Fun fact: Speak with Dead via Amulet of the Lost Voices triggers Tempestuous Magic every time. If you are nimble you can fly from one corpse to the next.
