Pros
Atlassian as a company has been doing very well, due to very high demand for its products. These products are all about team potential, team performance, team productivity so no wonder Atlassian itself is big on teams too. The place is full of great people to work with. They are great not only technically (check LinkedIn yourself) but also as great colleagues to enjoy working with. There is a strong balance and partnership among engineering, product management, UX design, and data analytics. Part of the growth in business comes from the original and very successful products like Jira and Confluence. Part also comes from the newly acquired products such as Trello and OpsGenie. There is a strong theme in this expansion strategy to keep unleashing the potential of all teams, starting with the tech teams. Atlassian is one of the unique companies whose values do make sense (check them out yourself) and there is a real strong focus for all team members to live those values. Part of every interview does also include a session on the value(s) you may most identify with and why. Atlassian is also a place for a new software engineer to get up to speed fast. The products are those exact ones (or similar to the ones) that you as a software engineer would be using in any company to develop your own products -- workflow management, internal wiki and collaboration, operations status, operations alerting, source code repository, etc. Knowing that your contributions make people like you far more productive is very satisfying. There is also real dogfooding going on at Atlassian as you end up using the same products for your development effort. If you get a chance to see how these products are used internally, you will amazed about the capabilities of these products -- unfortunately not well known outside, a mistake that Atlassian needs to fix. There is attention to detail in almost every aspect. For example, visit one of the Atlassian offices and you can see the difference. Go to youtube and find videos on the Atlassian founders. They are smart, passionate engineers themselves (with an Aussie accent :) and they get it right away whatever you are discussing. They can code very well too. There is a real strong positivity in the air at Atlassian. There is real caring for the teams inside or outside the company. The foundation donates a lot to the community and you can be part of that effort with your money and time easily.
Cons
Some teams may be divided across multiple countries so some of the usual problems due to remote teams may apply, depending on your team.