It's a visual feedback tool which makes issue tracking and agile project management a breeze.

So for me the best thing about DebugMe is the focus on the visuals. Their tickets are containing an editable screenshot and all the information your front-end developers need to fix the problems: the browser version, the screen resolution, the plugins used in the browser and the operation system too. Bugs and issues are also reported where they occur: live on-site. This makes it (compared to JIRA) super easy to report issues, give website feedback or create new tickets.

So unlike JIRA, it's not a general purpose ticketing system, and apparently of little use to anybody not working on front-end. Hardly an alternative.