This episode gets a '9' from me, only because I caught the preview for next week. Without knowing that next week we'll get to see what transpired since the plane crash, I would have been left wanting more. Instead, I'm now excited to see next week's episode. We know what the end results will be - for Mark, for Derek and for Arizona in particular - and I'm anxious to see how it all plays out.
I can't give the episode more than a '7' on its own, but knowing it's just the first portion of the story (and not the end of it) makes it a worthwhile episode.