I fly frequently from London to New York and San Francisco. The flights are quite fast - but here's the killer: in New York and San Francisco (and London if you aren't going near or via Paddington) - the trip from the Airport to my next destination - {hotel,office,client...} Can take 1/4 to 1/2 of the flight time!

New York is especially bad (2.5 hours at rush hour).

Would I pay a premium for speed of flight? Yes

Do I think that there are enough people to form that use case? Yes!

Will it work? No - the benefit obtained through a fast flight is obliterated by 3rd world airport links into the major airport destinations.

Concorde had a hard beginning - the French and Brits cooperating? On research?! (It uses the French spelling...)

But when you couldn't fly a helicopter to Midtown anymore, or into the City... The clock started ticking. (This last I have from dear old Dad who was in Finance in the Concorde era and through its end)