We intend to add a csv export feature next month. The first version will be simple: task title, description, type, estimate, creator, assigned to, and column. We'll improve on that with future releases, but will probably not add any support for file attachements and possibly not for message threads either. For now, you could rather easily export all the data yourself with a simple script using our API if you need to convince your CTO that we're not hoarding data and holding you hostage :)

If you have suggestions for useful reporting, please let us know. We're eager to improve the reporting options and the reports that you like would likely be useful to others as well.