I use iMovie for iPhone and used ReelDirector on the iPad when I had it.
I used ReelDirector for 30min. 9min was spent trying to figure out how to get the tutorial movie to run, 1 min to render that tutorial, and 20 min to wait for the render.
I stopped using it.
One change, JUST ONE CHANGE, and you have to re-render ................ TO PREVIEW IT!
It was simply UNBELIEVABLE that I had to render the entire movie to observe the change(s) I'd made.
Oh and it didn't export in a large enough format anyway, much less HD.
Maybe it has changed, I don't know.