Exciting times for a rapidly changing company
Pros
The company is working hard at all levels to bring positive change to the company culture, from a company wide adoption of Agile process, to culture shaping programs. They are actively trying to remove or reduce some of the roadblocks that impede productivity on a daily basis, and trying to adopt cutting edge technologies and methodologies while still maintaining the high level or service and security. The overall culture, at least in IT, is a LOT more relaxed and casual than it had been traditionally, which is good is you are trying to attract and retain good IT workers who have other choices in the market. Management, at all levels, are "just people" - approachable, friendly, not bigger-than-life or unreachable like in some companies.
Cons
With rapid growth and many recent (and coming) changes, there are naturally plenty of people that are resisting change. This is to be expected, and is not the fault of the company. It is a natural tendency for those who have been in one place for a long time to feel uncomfortable with that place changing at all.