As previously posted, several of use had IOs go into some detail on specific issues. In my case, it was my travel history with respect to my residency etc. However, it was not "bad" or "tough". I had all the answers he needed.
Others have some issues regarding legal matters (incl. tickets on rare occasions), marital status, tax issues etc. However, again, these are often not "bad" .... the IO is simply doing his/her job.
The critical lesson learned is GO PREPARED !!!!! See other posts for elaboration of this.