Pros
A lot of freedom on how to get things done. You can be really innovative and you'll be rewarded for it or you can just do what you are told, up to you. You are always encouraged to go to open source meetups and conferences and do one or more talks. If you have the right manager, the salaries and work conditions can be easily negotiated and improved. And of course, you get to work on open source all or almost all of the time.
Cons
Sometimes the work is not easy or just tedious and you have to push a few extra hours to get to the good stuff. Some of the manager and marketing teams are always pushing on not using opensource (thou being an open source flagship company), and are getting more and more power. Salaries are a bit lower than most, if you don't consider working on open source a plus.