Pros
You will work with the best of the best. Red Hat employs THE though leaders in Open Source and you won't find a group of more talented people anywhere else. If you want to work with the best this is where they are. Also, ethics are a priority from top down. Every company meeting I've attended where some other company did something questionable in the last quarter it was a priority of top management in the meeting to drive home the point that similar mistakes will not be tolerated and ethics must be foremost in all actions.
Cons
Benefits. They are clearly structured to be just good enough to keep people from leaving. This is surprising considering Red Hat's primary (only?) asset is the intelligence, skill and ability of the employees. To my mind benefits should be a priority for the company but come out to be barely average. This sadly seems to be by design because they understand the main motivation for new employees is to work with the most talented individuals in the industry. Before joining the company I personally sponsored may Red Hat employees to join my previous employer because the benefits were among the best in the industry.