Neil, I most definitely agree with your assessment of the value of using spikes.
That being said, I have a concern about the new design with the built-in spikes, even though I think it's a great new feature.
My concern is for travel. Even though the rubber feet fit over the spikes, so that no one would be the wiser looking at them, that the legs have spiked feet when the rubber tips are removed, carry-on x-ray will detect the spikes under the rubber, and sooner or later a sharp TSA TSO and/or security agents throughout the world will notice the spikes, reject the tripod from carry-on, and pass the word around to other agencies concerned with airport security in other countries.
My concern is that photographers will not expect their tripods will be rejected with the hidden spiked feet, and be unprepared for the consequences if they are rejected. At this time tripods equipped with spiked feet are routinely rejected from carry-on.
I would caution photographers with these new tripod to play it safe and remove the spiked feet while "in-transit," if the tripod will be carried into the cabin of a plane, even if inside a carry-on bag. Once at their destination, reinstall them.