Pros
I came in as a rookie dev, and due to the "open" nature of the company, i was able to learn a lot about many subjects. The perceived freedom and possibility to look at, and study up on, anything you encounter was great for my own experience. The mood at the office was casual, dedicated and motivated at the beginning. It was clear people cared a whole lot about the product they were working on.
Cons
then as you work longer and understand more and more, you realize the "open" nature is simply due to nobody knowing anything about the work process except for the release deadlines. Management seems to be running around with fire extinguishers without doing anything about the crazy guy running with the petrol and matchsticks. Then when you suggest taking down the root cause of the fire, you get a fire extinguisher pushed into your hands and asked to leave the building. But i see you asking: wait, isn't that counter-intuitive? giving you an extinguisher and pushing you away from the fire? Good question! maybe it's the top-down view i was missing in order to make it make sense.