Acting wise: Butterfield was Great, pretty much carried the film. (which is good because he had to) Ford and Davis were Good. Kingsley and the rest of the cast were OK. There was not much room for character development outside of Ender, and even he felt rushed.
Plot wise: It was too fast. They easily could have spend another 15 minutes or so developing relationships or showing more Battle Room scenes. Spend time in Salamander showing how Ender thinks outside the box. Spend time in Rat showing how effective Ender's ideas are. Spend time in Dragon showing his command superiority. And there was no reason to tip their hand several times about the ending.
Visuals: They were Great, as expected. However, they were confusing in the Battle Room scenes as you clearly see kids getting "flashed" several times but it wasn't freezing them. You really could not tell if someone was "frozen" until they told you they were. If we have to be told, why have the special effects for it at all? The special effects teams should have done better there.
Direction: Hood messed-up the ending. Here, less subtlety was needed. We need to hear Ender and Bean say what they are thinking. And the observers were just standing there having discussions like it was half-time when they should have been going crazy like they just won the Super Bowl. And Ender should not have spiked the football and done a touchdown dance because Hood never had Ender doing those things before. It was out of character. Also out of character was when Ender became the dual-weilding, Battle Room Bad-A** after just one shooting lesson from Petra. Instead of that, Hood should have had Ender just talk to Petra while observing the battle, pointing out where Bonzo was tactically inept.