Pros
I was a seven year employee of NI and had numerous promotions during that time. There is a pointed focus on developing employee skill sets. A lot of in-house promotions, too. Great onsite amenities, such as multiple cafeterias, gym, health clinic (sooo convenient), volleyball courts, and more. Easy access off of Mopac, and right across the street from the Domain. The ESPP program is fantastic - free money to those that take advantage of it. The culture is very strong in this company, it really shows. This is the only company I worked for that spent a significant amount of time correctly managing employees, from timely praise and attentive listening, to performance management when necessary. That's probably the one thing I miss most about working at NI.
Cons
Compensation policies. The bottom line is, fight hard for your starting salary. After that, you'll be subjected to an annual raise policy that, when they're given (some years not), are small bumps (2-6% on average). There is no level-setting of salaries once you are promoted.