Pros
Great place to start a career, especially for new grads. NI is big on ownership and responsibility. They like to give "meaty" features to new folks and see how far they get on their own. These projects receive support and oversight from leaders who tend to provide excellent mentorship opportunities to newer folks (your mileage may vary by department & manager). All facets of the organization (SW R&D, HW R&D, Marketing, Sales, ...) have some level of formal training to convert college graduates into productive members of the organization.
Cons
Most engineers work 45-50 hours per week, but some work 60-80 per week to "catch up" and never do. Many parts of R&D have temporarily (a quarter or 2) instituted 6-7 day weeks to meet project deadlines (rather than cut features). At NI-Tech (R&D's Internal Expo), they call up folks who have worked many nights & weekends, tell everyone else in R&D how hard they have worked, give them a plaque, give them a couple hundred dollar bonus, and say, "That is Engineering Excellence". I feel sorry for their family, children, and friends. This is a part of the culture I don't care for. Plus there are plenty of folks who put in nights and weekends who don't get recognized, likely because they have poor managers. Most of the management is young and inexperienced. Once you are experienced, you need to either buddy up with Senior Management, or get out. When you want to transfer groups, lets hope that your manager and the target group's manager like each other, otherwise it either may not happen or will take much longer than you think it should. Lots of power struggles among upper management. Many experienced folks leave to pursue other opportunities, such as better compensation. New products & features are celebrated and given plenty of resources. Quality and testing is talked about often but tends to get the short straw. Innovation seems to get the same treatment (more buzz than substance). There is plenty of buzz, smoke, and mirrors at NI (ask AEs about the Kool-Aid).