Avantages
I can honestly say MathWorks is a great place to work. Smart colleagues, fun environment, beautiful campuses. Everything is done very rationally and thoughtfully - I was surprised when I first started at how well thought out everything was. The company works hard to do the right thing and continue to improve (really living up to its core values). It's extremely collaborative, and you can always find someone to help or to bounce ideas off of. I don't find it to be at all competitive - we all want to help each other succeed. The company is privately held and the staff all benefit from its success.
Inconvénients
The downside of everything being so rational is that sometimes the processes feel too heavy and slow. But I prefer things being done the right way, slowly, than the alternative.