Pros
I get to work on a project I'm excited about and actually enjoy working on. The products NI makes get used for tons of awesome engineering applications. I feel like I'm contributing to something that is making the world a better place. The culture is relaxed, open and friendly. I like the people I work with and I feel like leadership generally makes good decisions. NI is very good about communicating with it's employees regardless of whether the news is good or bad. This gives me a lot of confidence in the company. Even when times are bad (2009 era for example) I feel like they try harder than most companies to be a stable employer and make decisions that balance the needs of the employees with the needs of the business.
Cons
I feel like I could probably be making a better salary elsewhere. To me personally, I feel like the benefit of enjoying coming to work probably outweighs the difference in salary though.