This was definitely a thing. First off, I knew without a doubt it would be a different work than the book, and that some stuff would have to get cut.
Up until the lake house, I was pretty ok with it. Last I heard, the movie was supposed to basically be a Bean/Ender buddy movie (they start to accomplish this by having Bean be in Ender's launch), but somewhere it turned into an Ender/Petra uncomfortable romantic thing. Not from Ender, but it was all coming from Petra. Ender was still majorly up in his head, but it was... uncomfortable at points.
After the lakehouse, things take a turn for the odd. 1) Ender is told that the IF is planning to invade the Formic homeworld, but not until some point in the future rather than just him going for defensive training. This kinda changes direction of the movie. He is told he'll still be using the simulator to train. Mazer's introduction misses one key piece of dialog - I will be the one programming your simulations. I will be your enemy (or something like that, I don't remember the exact quote). They just have him say - I will be your enemy, and kinda skip past the whole simulator part. 2) The place Ender will be on the simulators is a forward command base on a former Formic world. Yep, world, not Eros the Asteroid. I have a feeling they did this because a planet is a much better visual than a chunk of darkened rock, and to allow Ender to find the Formic cocoon without having to travel to a distant planet.
Other than that, I think they hit most of the major points of the book, with the possible exception of making Graff a bit more of an *** than he really is. Its not the worst book to movie translation I've seen (*glares at Eragon movie*) but its not the best.