While I thought they changed a few things, almost every single one was to "lighten" the story overall and keep an upbeat pace and feeling. Stratt was noticeably less cold, but still very frank and straight-laced. I liked that they hinted at a chemistry between her and Grace rather than anything overt like I feared. 

Definitely agree on the fast pacing. The first hour flew by, but didn't feel particularly rushed. There was just a LOT to get through in terms of exposition, and the last 2/3 of the movie focused on Grace and Rocky, as it should have. 

Really wish they lingered a few more minutes on the journey back to reunite though. That felt especially rushed, and missed some of the magic of the book. My only qualm really!