Avantages
Many opportunities for engineers - software, hardware, etc... Management encourages changes roles to find the right fit. NI hires talented engineers, so you rarely work with incompetent people. Work life balance is encouraged, and most managers are understanding if you have family, so you usually don't have to worry about working insane hours - except of course for the occasional release push. Also - Austin is a great place to live!
Inconvénients
Salary can be low compared to competition... but make sure you look at cost of living when comparing - Austin is a fairly inexpensive place to live. NI used to operate like a small company with limited bureaucracy, but they've grown which means that shared processes can sometimes get in the way of development. So far management has mitigated some of this, and I don't think it is nearly as bad as other big companies.