These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Acceptable Targets: A Russian anti-satellite missile test triggers a series of Disaster Dominoes that sets back every country's space program by decades. In Real Life, China was the only country to have conducted an anti-satellite missile test that created a space debris problem, it just wasn't as serious as this.
The reoccurring DebrisLeitmotif, for whenever the debris shows up, which sounds eerily like the Jaws leitmotif.
Fridge Brilliance: There actually is a very subtle clue that Matt's return towards the end was just a dream. Considering how he was usually depicted as being extremely professional, it does seem a bit strange that the real Matt would just open the door to Ryan's capsule and expose her to the vacuum of space without at least giving her a moment to put on her helmet.
Remember how Planetes made such a big deal of the horror of a Kessler Syndrome, which can potentially isolate Earth from space? More than likely, it's coming to pass by the end of the film.
If Stone had rested aboard the ISS for just a minute longer, she would have been caught in the fire, which engulfed the hatch to the Soyuz a fraction of a second after she went through. And if the fire hadn't forced her to evacuate when she did, she wouldn't have had time to flee before the debris cloud's second pass.
A more realistic scenario would have been even worse then that depicted in the movie. The expanding Kessler storm would likely not have reached the ISS, shuttle or Tiangong (since they all were in higher orbits), but would have made it impossible for any of their crew members to reenter without being shredded by it. They would have been trapped in space to slowly die, out of reach of all rescue. That all by itself would have made a good (but very different) movie.
Sci-Fi Ghetto: Destroyed. The film earned high scoring reviews from critics, became a box office smash and was nominated for 10 Academy Awards, 7 of which it won (including Best Director for Cuarón).
She Really Can Act: As odd as it sounds to say about an actress with a long career before the film that included an Oscar win, many had this reaction to Sandra Bullock, as she was mostly regarded as a lightweight romantic comedy star.
However, her role in this movie is also similar to the one she had in Speed, early in her career.
Tainted by the Preview: A number of detractors and reviewers have decried the movie's "lack of scientific accuracy" based merely on the presence of sound in the trailers, and on using those same, pre-release trailers to make snap judgments about the nature of the emergency, the fact that the ISS, the Hubble, and the Tiangong are in the same orbit, or that an astronaut being flung into outer space could possibly be panicked.