In a word: awesome!
In a phrase:go see it as soon as you have a chance.
The fact that they managed to pack the entire book (with a few insignificant changes) into less than two hours of film was mind-blowing. It's slightly random if you have not read the original novel like I have, but I doubt anybody would get lost. Half of my statements on the trailer review I did with James Starslayer on his blog a couple months ago turned out to be way off base. I am glad. See my post on why this should be a longer movie; I rest my case. Bullies, check. Ender's team/Bean, check, although they didn't so much introduce them as throw them into the same room. Ender's first battle room scene, check. And then they combined all four of Ender's major battles as a team leader into one, which worked out well. The ending sequence was done well, alhough they left out some major depth in the middle of it. There's not much more to say since there are a lot of surprises in the story.
the trailers we got before the film were Desolation of Smaug and Catching Fire. The DoS trailer blew me away since I was finally experiencing it properly, although I still could not make out Smaugspeech, though that is my problem. The CF trailer looks cool too. This was the second one, which is a lot more compelling than the first.
Go watch Ender's Game and yell at me later1
p.s. the part I was most disappointed with, unlike most movies, was the original score. I expected the music to dominate some scenes, but it kind of hung in the background untill time came for the end credits.