Are you incorporated? If not I've been told a carnet is unnecessary, but it can be up to the individual agent to decide if he or she wants to make your life hell or not (this is paraphrased from what I was told by a sympathetic agent after a less than sympathetic agent decided he wanted to demonstrate his power).
Not incorporated. But traveling with 4 or 5 cases equalling maybe 300lbs and $20k to $30k value. You're sure right about it coming down to which agent you draw!
Each time I've tried to find out from the Customs Office what is necessary I've gotten different answers.
I think I'm going to give David's method a go. I'll be going abroad at least once, maybe twice, next March. This'll be incentive to get my gear packed and flight-ready before the last minute!