Lots of great things but lots of room for improvement
Pros
Several of the products are legitimately "best of breed" with tens of thousands of customers that genuinely love the product. A chance to work on something that really helps teams, as opposed to something that sells ads. The company values mean something. Sure, not all of them. (No one seems to really agree on what Build With Heart And Balance means.) And not 100% every day. But overall, the values drive the company more than most. Many of the executives really care about having a great place to work. The "Experience Team" does a fantastic job of making every-day life at work pretty good, whether it is big events (like annual friends and family day) or small events (like "sillybrations" on wacky quasi-holidays). For most people, there is a pretty good work-life balance. Most people work 9-5. Almost no one works weekends. It is a big company with many projects and teams, so this can vary somewhat. But if you walk around the office at 6pm it is pretty empty. Atlassian has pretty modern product management practices. Yes, there is room for improvement. Yes, there are companies out there do it a better or more consistently. But if you read any book or blog on modern cutting edge product management you'll think, "Hey, Atlassian has been working like that for a while already." The vast majority of your coworkers are smart and have their hearts in the right place. You will rarely feel like you're engaged in turf wars or politics or working with deadweight.
Cons
Salaries are flat out low relative to the talent levels and amount of equity given out doesn't fill the gap. The current weakness of the Australian dollar means jobs everywhere else in the world look appealing. Moving to Australia is a big draw but it is near impossible to get senior talent, especially from the US, to consider moving. There are a lot of teams. Quite a few of them are not an ideal choice. Either because they're working on an also-ran product, because they're strategic priority #42, or because they're dealing with morass of cross-product work. For instance, you can work on billing systems at Atlassian...or thousands of other companies. Some people and positions do not have good work-life balance. Often this comes from Team Leads or other more senior developers who put in long hours. Sometimes this is due to lack of training in delegation skills. Other times it is due to skill/expertise gaps. (When you grow this fast, you might be the only person on your team who has been around long enough to understand how that subsystem works.) Quite a bit of silo-ification between products and geographies. That's somewhat understandable as the company has grown but it was a problem even when it was substantially smaller. This is a bit ironic given the tools that Atlassian makes. I doubt this is unique to Atlassian but Product Management reigns supreme (over design and engineering). PMs are the ones who have meetings with the CEOs and GMs. There has been significant turnover among PM ranks and the general consensus is that the PM discipline has stagnated since a reorg from a functional structure a few years ago. The failure rate of new hire PMs is staggeringly high compared to any other role in the company. Engineering and Product Development is a strength but many other functions have lots of room for improvement. HR is a perennial sore point for many. Lack of training and career progression have been a top complaint for years and very little has improved. Rollout of new systems (like applicant tracking systems) and processes takes just as long as at many other companies. There's no two ways about it: legacy code. The main products are over a decade old. Atlassian has done an admirable job of maintaining high R&D investments (instead of turning them into cash cows with skeleton maintenance crews). But you'll be working on 13-year old Java download applications. The company is in the midst of an existential shift to find its way to a SAAS future but there's a huge gap between the products as they are today and how a product built from scratch would look.