Of course the Terrafugia isn't the answer - how can it be if it is not also a boat!
There is some modest hope in this direction -- the Icon A5. It's more a flying boat that also has wheels, but still:
When I was in architecture school I had a graphic design business for beer money. One day an earnest engineering student came in wanting a brochure made for his flying car company. He wanted to pay in stock instead of cash.
Remembering that the lawyer who handled Henry Ford's battle against the Selden Patent was paid in stock, which allowed him to switch careers from attorney to philanthropist, I thought, "what the hell," and did the brochure. But I told my roommates, "this will never fly. If you think traffic jams are bad in 2 dimensions, just imagine rush hour in 3 dimensions. The death rate will kill the idea as soon as it's tried."
Even if flying cars could be built of glypsite* and powered by glyptonium**, the idea that the mass use of flying cars would not create aerial havoc is not really believable. Oh, the insurance rates!
* glypsite was a fictional material devised by the architecture students--it was transparent, weightless, with infinite structural capacity at infitesimal dimensions. Our standard response to the professorial question of "and how would you build that?" was "We'll use glypsite!"
**glyptonium is the energy analogue to glypsite.
Your reader, in "The Heartbreaking Truth About Flying Cars" is an urban purist, and an environmental activist. But he's off base on the value of blending a car and an airplane, even if it's a "lousy" car and airplane. Most of us appreciate the car and airplane for transportation, and most of us might be interested in an airplane if it werent for cost and safety concerns. I dont think that I'd mind mediocre handling as a car or a plane for a vehicle that has some abilities of both. As for safety, a lot of the safety concerns come from bad weather, and roadable airplane is an excellent way of avoiding the necessity to fly in bad weather.
If the Terrafugia includes well-developed avionics that are internet-enabled, thereby making weather, traffic and safety information readily available, then you have the makings of the simplification of flying, which is very important to introduce it to a larger customer base. Remember that most auto consumers buy their cars on how generally useful they are. I bought a small SUV 11 years ago and I'm still driving it. It's very useful. I think that the Terrafugia should be viewed in that light.
Regarding cost, I think that if it's successful, the cost can come down significantly.