One thing that irked me....
was the casting choice for the young Ruby. She was like 3 or 4 shades darker than Stenberg. I know it shouldn't matter but it's a pet peeve of mine when younger versions of characters aren't believable looks-wise.
I'm glad the young actress booked the role considering she was probably the best actress.
As a sidenote, I think the best example of cross age casting was Henry Cavill and the actor who played young Clark in MOS.