Pros
This is a great company to work if you want stability and flexibility. Expectations are quite low and even showing up is not required. If you are unwilling to grow or learn, you won't be forced to and can sit in your comfortable isolated box for as long as you choose, so long as you aren't completely incompetent for an extended period of time. You might find a project you enjoy and have no risk of anything changing for as long as you want.
Cons
The company's business model was built around growth, which has not occurred in over 10 years. Since they are unable to make any tough decisions (focusing efforts on profitable areas rather than wasting many man-centuries rebuilding non-growth products from the ground up, trimming the fat, etc...), they try to have their cake and eat it to. There is a cult-like mentality with complete denial for any negative aspects of NI's products. Since nearly all employees and management have only worked at NI, there is a tremendous amount of group-think and any outside ideas, including keeping up with the times, are heavily shunned. Any action takes a tremendous consensus, as individuals are never put into a position of ownership. This leads to a lot of time wasted trying to convince even the most minor stakeholders of the importance of your ideas while trying to maintain the support of those you already gathered as those who disagree with you will campaign against you. It becomes a war of attrition and the most stubborn end up winning. This can be very tiring if you try to fight for something. Anyone with any sense leaves after 5 years, and those that are left are the ones who are too afraid to change, those that are unwilling to grow, or those too incompetent to find other employment (or the rare few that are highly value flexibility over any kind of career growth or compensation). The company is extremely stingy in all aspects. This becomes ingrained in you. Spending money on anything is the biggest sin at NI. This is apparent from the mandatory shared hotel room policies for travel, poor equipment used by engineers, down to salaries. NI either is completely ignorant of market forces or simply does not value employees by offering below market salaries in the hopes that being able to wear shorts and sandals to work is somehow worth tens of thousands of dollars per year as a perk. Good performance is rewarded with promotion freezes. Promotions are awarded with nothing more than a title change (no salary changes!). Raises are becoming more infrequent and cutting them are the first line of defense against the ineffective business plan developed and executed by management. It makes you wonder if the slackers were always that way or just realized there was no reason to do anything other than slack. Management has many intelligent people, surely who understand the consequences of these policies. This means they will tell you one thing about their values (valuing people, honesty, etc...), and do something completely differently. They act like there is going to be growth around the corner when in reality, the company has simply turned into a value company trying to do things as cheaply as possible with replaceable cogs.