The migration from E9 to E10 moved the Data Card sets that were under Events and Surveys over to the Custom Objects area and also creating new CDO sets there as well.
What I am finding is missing functionality that makes my life so much easier:
1) the ability to map en masse all unmapped records. You could do this with literally a push of a button in the Data Card area.
2) the ability to delete en masse all unmapped records. You could also do this in the Data Cards area as well.
Map or delete all unmapped custom object records