I actually found the episode enjoyable myself. Up to a point. After Charles Clay gets killed it kind of goes downhill. I thought the ending was a little bit hokey with Swanny's 'tisnt'. And poor Mac explaining everything to the crowd. Columbo had to continually correct him.
I've grown fonder of this episode over the years, due to its quirkiness. I especially enjoy how Columbo annoys Mr. Charles Clay at every turn ("Japan is... THAT way???; putting his arms around him; stuffing him into the car) and Robert Vaughn's delivery of several lines ("I like everything... PRELIMINARY")