Pros
I found the people and the open culture to be the best part of the company. From onboarding to exiting, it was a really awesome experience. They'll do just about anything to make you feel comfortable and "ready for action".
Cons
In my very short period of time - there is a sense of entitlement among the younger staff. Atlassian provides food, drinks, icecreams etc - and I still heard people b**ching during lunch time. It's growing to fast that half the staff have only been at the company for less than a year - so the knowledge base has been diluted a bit. There is a huge amount of "cult" or culture - especially around work/life balance - but I did feel as if I was being monitored, and having a regular schedule of in/out was a no-no. So if you have a family, make sure you discuss the very real potential of spending a serious amount of time in the office with them.