I used Level 4 of the OT Overview with my 7th grader this year. The research aspect is fantastic. Using a topical Bible, a Bible dictionary and a concordance, the lessons include specific things to investigate. I think this was my son's favorite (or second favorite -- he liked the stick figures too) part of the study. I loved that the research aspect was so easy for me to implement.
My complete review can be found at debrakb dot blogspot dot com, go back to August 2009.