I had read the story before and I saw the movie this evening. I wrote to a friend that it's about 25% Ted Chiang and about 75% Hollywood (with some very significant changes, though a similar central theme).

I guess discussing the differences makes for a huge spoiler. Perhaps I can say that the movie has a major plot about military conflicts (obgu orgjrra uhznaf naq urcgncbqf, naq orgjrra uhzna angvbaf) that's absent from the original story. Also, in the movie we learn jul gur urcgncbqf ivfvgrq Rnegu, whereas in the story guvf erznvaf n pbzcyrgr zlfgrel.

In the story Louise ersyrpgf n terng qrny ba jung vg zrnaf gb xabj gur shgher naq ubj guvf vagrenpgf jvgu serr jvyy, while in the movie this isn't really depicted at all, except sbe gur prageny cybg nobhg xabjvat gur sngr bs ure zneevntr naq ure qnhtugre nurnq bs gvzr.