Pros
I have been there for a long time (25 years now). NI went through different iterations. I like the direction of the company lately (past 5 years ish?). They are trying to modernize their management style and pay their employees more competitively. Every year software engineers can choose what groups to work in, and most move groups. Lots of possibilities to learn new things. If you don't like it, at the most you'll suffer a year till the next shuffle. The management tries hard to manage well and actually help the engineers produce value. One thing that is always constant: I generally like the people I work with. My co-workers are awesome and smart people. Most of them work well with others.
Kontras
The pay wasn't always competitive, but they have been trying hard to rectify this for the past couple of years.