I have been using MSP and JIRA for a few years now and they way they currently exist, I see them as complementary products. JIRA is great for development teams to manage and collaborate on their tasks. From a project management standpoint, the reporting capability has both strengths and weaknesses. It has a very powerful query language; learning that takes some effort, but it is well worth while. We use these filters, alongside JIRA boards and Dashboards in our project status meetings very effectively. The weakness though is in the stakeholder reporting and I have found I need to replicate the JIRA data into MSP in summary form, to use MSP’s reporting features – that approach is especially effective with custom fields. We will be trialling Portfolio soon, which is another Atlassian tool so sits on top of JIRA projects and I’m hoping that will save me the effort of dual entry into MSP. I see there are quite a few 3rd party tools as well, for adding Gantt chart functions to JIRA and also connectors that create a link between the two products. As they stand though I use them both and set them up to leverage the relative strengths of each.