I wouldn't say Atlassian has worked to make a great unified UX. I mean, they tried, but using their products makes it painfully clear that they just glued togeather a bunch of disparate projects. For example, each product supports different markup languages (or none at all) with different editor buttons and shortcuts and so on. Even the github ecosystem feels more integrated, because everyone just follows the broad strokes of what github does with its UX and integrates with it.