After using Pivotal Tracker myself for a couple of weeks, I recently migrated our complete development from Mingle to Tracker.
Migrating existing data between tools using CSV is always a pain. It starts with Mingle using tabs as a separator instead of, well, commas. Of course, you have different field names to match up, and then there’s the difficulties of making MS Excel write a CSV file with commas as separators instead of semi-colons. To avoid all that, I put together a super simple Ruby script to convert a Mingle export into a valid Tracker import: