We have a lot of custom post types created manually and have several meta boxes attached to these custom post types. I have looked at Piklist and it does look interesting however I am concerned about being able to migrate so not to lose existing data held within posts.
@mojowill– In most cases the data is not unique to the metabox system. Piklist should be able to pick it up. I suggest you use Piklist WITH your existing system so you can verify the data is correct.
When setting up Piklist just use the same field names you used with your existing system. You should see the same data in two places. Once you verify the data is correct you can deactivate your old system.