Pros
Atlassian are very much a values based company - it's a core part of their interview process and something that permeates into your day to day working once you arrive. If you don't know the values then definitely read up on them as if they're not for you then neither is Atlassian. This is a place where you can really come in and make the changes you think are required to make impact in your job, there is lots of existing status quo but it's all able to be openly (and respectfully challenged). They care a lot about their employees, and even during COVID are going above and beyond to ensure that we're having as good as an experience as we can do by running lots of trainings, team events and budget for social(ly distanced) entertainment.
Cons
Chance can (and does) happen quickly - it's always well rationaled, thought out and communicated but if you find yourself caught up in the midst of it can feel rather daunting and chaotic and you can feel rather like a fairly small piece without control of your professional situation. They are a very large (and expanding) company and this means that there are lots of information sources to get your head around, and it's easy to miss out on important updates if you don't have a good routine of news gathering. Without that you spend all your time reading up on things and not progressing on with your work (if you allow it, or can't stand not knowing about things happening).