The book was fun and intriguing, but I was worried about whether its journalistic format would adapt well to the screen.
Clearly, I need not have been concerned. Ridley Scott's The Martian may be the best movie about near future space travel since 2001...and it's harder science fiction than that. Matt Damon plays a challenging role in which he's often acting to a screen, and does it very well. And while some of the challenges Watney faced on Mars were cut for length, the amount of sass and snark remained exactly where it should be. The contrast between the attitudes of the Houston workers and the JPL guys convinced me that some people from NASA were intimately involved in the project - not surprising given the movie did have something of the feel of NASA propaganda.
The biggest flaw was the ending. I felt it would have been much stronger if ended a little bit sooner - the movie essentially had two epilogues and that's pretty much always one, and sometimes two, too many.
The visuals were awesome. The scenes on Mars were filmed in Jordan rather than the usual suspect of the American southwest, giving a location less familiar to viewers, and then seamlessly woven in with excellent digital mattes. The Hermes was simply gorgeous and almost made me yell "Yes" right there in the theater when it showed up on screen for the first time. The design looked vaguely familiar, but I'm not able to place where they might have got it from. Or maybe it just looked so much like a relatively small interplanetary ship should look like. The Mars suits seemed about right too. Overall, it was a visually gorgeous movie.
If you've read the book you'll understand this: Commander Lewis provided the soundtrack.