Designers, QA, support and managers are typically already using a VCS, and usually it's Git. And if they don't, this is as good as ever a chance to start.
From QA perspective, which is the one the closest to me: I wanted such a tool for many years, and even though I haven't tried this specific one, I endorse the idea with both of my hands.
In the context of QA, it's always a problem to coordinate between test development, feature development, feature description, and tracking the work progress. All bug trackers I used to date are awful at it. This has a potential to solve at least part of the problem by being physically connected to the work done by either development or QA, or, ideally, both. The holy grail here is the ability to determine what tests to run in response to a commit without making it too much of a burden on the committer.
Tests can easily be the most expensive ongoing activity a development company may undertake. In this context, being able to avoid running useless but expensive tests is very desirable.