I've been playing around with an early access version of Mingle on and off for the past week (even if early access only means one month before the general public).
I've got to say it's a really nice program. Yes there are a few minor quirks but it's a great tool for managing scrum under the right conditions. "What conditions are those?" I hear you ask. You need a team where most people are remote. If you've got a co-located team and everyone can be together at the same time then a tool like Mingle is, in my opinion, only useful for the Scrum Master (or project manager). Using a tool like this as the primary coordination tool for a team takes away from the essence of what makes Scrum, XP and other agile methodologies tick; that being the human interaction and team work that occurs when people are literally standing shoulder to shoulder working towards a common goal each day. The physical aspect of a wall covered in post-it notes and a half dozen team members standing within 3 feet of each other and communicating about those post-it notes can never be underestimated.
Software like Mingle, Scrumworks and others remove the wall as the point of focus and try to replicate it on screen. Mingle even has a screen that looks just like a taskboard. But where's the collaboration or even the fun in crowding a team around someone's monitor and trying to update task descriptions or story cards in a software tool. And how often is that even going to happen in reality?
That said, remote teams will get some benefit from Mingle. It's a good web based tool, quick and easy to use (and that's the most important thing), it keeps things in sync across team members, backlogs, etc , has a nice dashboard and looks to be an effective tool at managing backlogs and sprints without dictating exactly how those backlog items are delivered or how the sprints are run. For example, out of the box mingle includes project templates for XP, Scrum and "an agile hybrid".
The one thing that bothers me is that there doesn't seem to be an obvious link between dates and iterations, or a concept of what the "current iteration" actually is. The iteration view shows all iterations unless you manually set a filter and that filter has to be set by individual team members. It just seems to me to be an oversight.