I used Mingle before in a very large project. It was good enough, but soon I moved to a smaller project (4-7 people at any one time) and switching to Trello has

I used Mingle before in a very large project. It was good enough, but soon I moved to a smaller project (4-7 people at any one time) and switching to Trello has proved to be a real asset. We create cards (story cards, basically) for each user experience and move them to different columns (Backlog, In Progress, Done) and then archive columns at the end of each Iteration. We also have Known Issues columns and we maintain a large amount of our discussions about implementation on cards. Also as the developer on the project, I find it useful to put the individual tasks of each user experience on the corresponding cards, which I can split into lists (such as 'API Tasks' and 'UI Tasks'). It's very flexible, and I've found it to work very well with the way I intuitively do things. I also use it on a small side project that I do with a colleague of mine. We love it. Everyone with whom I work on Trello loves it and we avidly follow its development.