Here are some of the answer of this question by a former employees of SpaceX,
I've been an engineer with SpaceX for over five years now. I've seen and helped the company grow from less than 500 people in to the powerhouse it is now. I highly doubt that there is a cooler company in the world than SpaceX. Everything that's been said is certainly true. SpaceX really is awesome. What's been said is just one part of what it's like to work with Elon Musk so I'll discuss the side that you won't often hear.
If you want a family or hobbies or to see any other aspect of life other than the boundaries of your cubicle, SpaceX is not for you and Elon doesn't seem to give a damn.
This side of what it's like to work with Elon shows that no one likes working with Elon. You can always tell when someone's left an Elon meeting: they're defeated. These are some of the hardest working and brightest people in the world, mind you. And they are universally defeated. At least in engineering, who knows what HR and finance does.
The reason for this is that Elon's version of reality is highly skewed. It's much like Steve Jobs's "reality distortion field" except Elon isn't great at public speaking. If you believe that a task should take a year then Elon wants it done in a week. He won't hesitate to throw out six months of work because it's not pretty enough or it's not "badass" enough. But in so doing he doesn't change the schedule.
One of the most famous quotes that runs around the office is one from a company wide talk Elon gave a couple of years ago where he said "Not enough of you are working on Saturdays." Of course reality kicks in and either junk product gets flown or something terrible happens. Ultimately the schedule slips--surprise surprise, fatigue is real.
It's understandable. Putting people on Mars is not a small task especially given the overwhelming political obstacles that face SpaceX's mission. Continuously being the underdog, fighting the ULA behemoth and the entrenched politicians that strangely want SpaceX to fail is only a small part of it. SpaceX certainly requires a hard mentality. But so often Elon's leadership is best compared to a master who berates and smacks his dog for not being able to read his mind.
Nothing you ever do will be good enough so you have to find your own value, not depending on praise to get you through your obviously insufficient 80 hour work weeks.
In order to continue working with Elon, you have to learn to ignore almost everything he says and you have to be prepared to be jabbed over and over. "Just six more months and we'll go IPO!" is among his most repeated lines though he stopped trying to sell that a couple years ago as people stopped believing it long ago.
It is a great company and I do love it. But it isn't the pie in the sky, everything's great idea that so many seem to think.
