I did a CBP and CIS FOIPA, I think. And maybe FBI. FBI had nothing on me (that they could share, anyway). The other two had entry and exit records, old applications, all correspondence, etc. I guess it's useful in general. For example, the entry and exit records will be useful when I apply for my child's CRBA. But, I think you can wait until you naturalise, and then do the FOIPA with CIS so the record will be complete. It can take upto a year, anyway.