This was originally written about the book, but the movie has the same storm scene which is what this answer was about. It was a really gripping story, I greatly enjoyed it, and had enough hard science to be very satisfying. And was a real page turner, I think I probably read it all the way through in one go until I finished it :).

But it did have quite a few improbabilities. Especially, the dust storm at the beginning. Let me explain:

The highest speeds are probably in the dust devils. Can be up to 45 meters per second or 162 kilometers per hour. HiRISE Clocks Hurricane Speed Winds In Martian Dust Devils

That's easily fast enough to count as a hurricane on the Earth. However the strength of the wind depends not just on its speed but also the density of the wind.

ONE HUNDREDTH DENSITY OF EARTH WINDS

The density of the Mars atmosphere is far less than Earth's. This varies between day and night and between summer and winter and depending on altitude. It is greatest at the bottom of the Hellas basin in the northern summer. Roughly though, it is about 1% of Earth's.

So, that means, that the winds have a hundredth of the mass, and energy, they have on Mars for the same velocity.

EQUIVALENT TO WINDS OF A TENTH OF THE SPEED

Or, putting that another way, to convert those 162 kilometers per hour winds into Earth equivalents - since kinetic energy = mass * velocity squared, then that hundredth of the mass means winds there have the same kinetic energy as a wind on Earth at a tenth of the velocity.

So - that 162 kilometers per hour on Mars is roughly equivalent in its effect to 16.2 kilometers per hour on Earth in terms of its kinetic energy.

Even if you were stood right in the middle of a dust devil, you'd feel roughly the same strength of wind blowing past you that you'd feel on a gentle cycle ride on a calm day.

Astronaut caught in a Martian dust storm as imagined in the BBC Space Odyssey (TV series) - 27 minutes into the DVD.

And another screen shot from the same TV series of the astronaut standing unperturbed as the dust devil passes by - so this is a movie that got it right.

ANALOGY TO EXPLAIN WHY THIS IS

If someone is throwing five pin bowling balls at you, at say 20 miles per hour, and lots of them, say 10 a minute, you'd notice it.

If they throw ping pong balls at you at the same speed, same frequency, you'd hardly notice.

It would be roughly equivalent to throwing the five pin bowling balls at you at a much slower speed.

Table tennis ball mass 2.7 grams

Five pin bowling ball - mass 1.588 to 1.644 kilograms

In fact, a ping pong ball at 2.7 grams and 20 miles per hour has same kinetic energy as a five pin bowling ball at 1644 grams and 0.81 miles / hour ( 20*sqrt(2.7/1644) )

That's very slow, would be hard to actually throw it much distance at all at that speed. It's more like, if they are holding it in their hand and swing it gently back and forth and accidentally hit you with it as they do so. You'd feel roughly the same impact as you'd feel from a ping pong ball thrown at you as fast as they can throw it.

Well it's like that. We don't have much experience of being hit by very light things at 160 km / hour which is why I am using these everyday examples of much heavier things thrown at slower speeds.

STRONGEST WINDS ON MARS ARE EQUIVALENT IN STRENGTH TO BEAUFORT LEVEL 3, GENTLE BREEZE

On the Beaufort scale, it's equivalent to level 3, gentle breeze. Enough wind so that small twigs start to move about and the tops of waves at sea begin to show a little bit of white. But it's not quite enough to raise dust or dead leaves in autumn. That's Beaufort level 4.

Beaufort scale

Even the strongest winds won't be able to blow away significant parts of a rover or damage the solar panels.

ENOUGH WIND TO DISTURB AN AUTUMN LEAF?

The very strongest gusts of winds on Mars, right in the middle of a dust devil, wouldn't be enough to disturb the position of an autumn leaf if there was one on the surface at least not under Earth gravity.

If you put an autumn leaf on Mars, 40% lighter, perhaps there'd be enough wind in the strongest gusts of a dust devil to gently blow it across the surface.

EXAMPLE UNDISTURBED PARACHUTES

As an example of this, the parachutes from our landers on Mars remain on the surface just where they landed for years on end.

This image may identify one of the parachutes of Beagle 2 which has remained undisturbed on the surface for about a decade. You wouldn't expect it to be moved by the Martian winds as they are just too weak for this.Beagle 2 spacecraft found intact on surface of Mars after 11 years

Indeed the dust devils have proved to be useful by cleaning the dust from the solar panels. And they can only do that because the Mars dust is extremely fine, as fine as cigarette smoke. They couldn't pick up ordinary Earth dust.

The average dust particle size is of the order of 1.6 microns.
Dust on Mars - University of Copenhagen You would need a microscope or hand lens to see the individual particles. This Mars dust is similar in size to the dust in tobacco smoke and average sized bacteria. Particle Sizes

HOW THE SAND DUNES WORK - BECAUSE OF MUCH LOWER GRAVITY

The sand dunes are impressive looking as if they were results of much stronger winds. But the larger particles in the dunes move through "saltation" where the particles do not get taken right up into the atmosphere but instead move on ballistic trajectories - of a few hundred meters (far further than on Earth) - this moves particles of up to mms scale that are far too large to be lifted up into the atmosphere. Giant saltation on Mars

The huge moving sand dunes there are a result of the lower gravity, which lets the grains of sand move more easily without ever being taken up into the atmosphere. So that again gives an impression that the winds on Mars are stronger than they are.

UNDERSTANDABLE MISTAKE

So it's an understandable mistake to make. But it's a mistake all the same.

Then, the idea he could sustain himself for so long by the methods he used I thought was wildly improbable.

But, as I said, enjoyed it, just suspended disbelief, much as you do when you get Star Trek books talking about transporters and hyperspace. So, this is a Mars where the winds can blow big things away beyond the horizon. Adds to the drama, makes it a more exciting story.

Okay it's not quite the Mars in our solar system, but can enjoy it all the same and enjoy the techy details he did get right. And things like how he eventually communicates back to Earth are really clever and ingenious and a lot of fun. That was the best bit of the book for me as far as hard science goes :).

UPDATE

Peter Voelkl says in a comment, it's an intentional "mistake" he did for plot purposes, i.e. a bit of artistic license.

He explains it 14 minutes into this interview here: Triangulation 163: Andy Weir from Triangulation (MP3)

Also at 32 minutes into this

He mentions some more things in this interview with Adam Savage of Mythbusters

At 9 minutes in they discuss how his spacesuits can be put on by one person unlike present day ones and how they are flexible so you don't have to e.g. use tools to pick things up from the surface as the Apollo astronauts do. But that's more like extrapolation of current technology.

As 36 minutes in he mentions a mistake he did with reducing Hydrazine, exothermic reaction a chemist says that - in the book he gives enough information to calculate the temperature increase of the hab to do it over the given time - it would have heated the hab by 400 C roasted him alive, too late for him to correct it as it was already in print. A million ways he could have fixed it.

At 39 minutes in he mentions another error - that he didn't know you can just bake the CO2 out of lithium hydroxide canisters.

This is a copy of my answer to: How realistic is the book "The Martian"

I don’t suggest that they are merged since this one is about the movie, not the book and this one is particularly about the science, while I suppose the other one could cover many other things such as sociology and psychology of it.