I just finished my talk on moving from CCK in D6 to Fields in D7, and promised to post my slides, which are full of references to the relevant issues. There is no place to do so on the DrupalCon session, so I'm posting them here.
For reference, the session description was:
Fields in Core will be exciting and powerful, but we still have some work ahead of us. Now it's time to figure out how to get there from where we are now. Hundreds of developers need to update their CCK-related modules, and thousands of administrators will need to update their data. Plus not everything about CCK made it into core. Which modules and functionality were left behind, and why? Karen Stevenson, one of the CCK maintainers and part of the team that got this code into core, will talk about the upgrade path and the 'left-behinds', and what those of us who have been using CCK in Drupal 6 will need to do to adjust to Fields in Core in Drupal 7.