I've always liked this episode. Roddy McDowall is perfect for the character the writers created. If you notice, the Villain in the early Columbo's were usually some actor who was "hot" at the time. Planet of the Apes, Beneath the Planet of the Apes, were po****r at that time, Kim Hunter was in Suitable for Framing shortly before this episode.
My only complaint, but not really a complaint is, continuity in the driving scenes (with the bomb) While driving in the rain, talking on the phone, it's clearly a nice road, you can even see curbs. but the road in the daylight after the bomb went off, the road is like some old abandoned logging road barely paved, big rocks on the road, just doesn't match.
Also, as an amateur Photographer myself, It always slays me in these shows (not just Columbo) when someone is taking pictures indoors, they aren't using a flash. Sure you can use fast film but still not in that lighting and I'm sure Roger could afford a better, faster lens. A Nikor F2 isn't that fast, the F1.4 would be better, and at one point he switches to a 135mm lens no tripod, etc... And the biggest flaw that always irks me is they never focus. they just point and shoot...