I haven't migrated. However, since MS at last is putting some effort in a new Planner app I sincerely hope they will look to Trello. I would not migrate if I were you. Until you see the last version of Planner. For instance Planner does not have the possibility to assign check list items to persons, or set dates on check lists. This is a great option in Trello I think (I used to use Trello prevoiusly. Not any longer) I'm currently trying to get Planner to work.
