The biggest problem I see in the trailer is that they make Ella be some Jackie Chan-esque girl, when in the book there's none of that. She's the kind that solves things with her brain, and they seem to be making it into an action flick for kids. Certainly there's adventure, but she gets herself out of troubles with ogres by using their persuasive speech against them, not by beating htem up. That, and they seem to have added something about someone trying to take the Prince's crown, and I don't remember that happening.
The problem I have with kids' books made into movies is that so often the movie makers believe what's in the book isn't enough. Certainly you need to add things so that it's not just the same thing (look at Harry Potter), but I think you can interpret while still being true to the book. You certainly don't have to add bathroom humor for it to be appealing to any audience, kid or adult, which is my biggest annoyance when it comes to movies made for kids. I think Holes and LotR are the best examples of books interpreted well as films, but usally it's more disappointing than not.