I've only floated across the line twice in the Hyena ('88 Westy) during our wanderings in search of dinosaurs last summer.

At one of the crossings, the U.S.A. customs officer looked in the fridge, remarked that it was actually cool, and removed my son's bag of carrots indicating we were not allowed to bring fresh produce across the border.   When the 3.5 year old hollered, "Hey, those are my carrots!", I figured we were headed inside.  The agent froze for a second, looked at the boy (who, after several hours of travel, looked like he might come unhinged), looked at me {I shrugged my shoulders}, then put his fingers to his lips (Shhh!) and put the carrots back in the fridge.

Relatively painless.

Twenty-some years ago, a group of us crossed the boarder into the U.S.A. in my '66 Westfalia - it took three hours - during which I was questioned several times about the amount of tools they had found under the rear bench.  They bought in a dog and crawled through every inch of that bus.  When the agent was down with his head stuck under the engine compartment, I non-chalantly remarked that it had been some time since the engine had the valves set and asked if he wanted to take care of that while he was under there (That man didn't have an ounce of Ha Ha).