As you said yourself above, some people flying Emirates might say "what aircraft type on my flight" in order to get the best "cabin", but the vast majority won't even really consider this, assuming all flights/facilities to be the same, and instead will book based on timings and fare.

Do people book based on "cabin"? Yes, a small few. Do people book based on "aircraft"? Yes, an even smaller few, though obviously not consistently. Even if just to be able to say they tried a new aircraft type.

I would LOVE to have flown Concorde, and my choice would have had absolutely nothing to do with the tiny, 2-abreast seats, the poky cabin, the timings and shorter flight duration, or the fare. It would solely have been a) for the experience, and b) to tick off another aircraft type.

That said, I have met a few obnoxious types who will not fly on Airbus aircraft (one was Australian, the rest American). For them, it's Boeing or nothing (not sure how they'd react to an Embraer or anything else non-European).

With KLM (as the last passenger operator) planning to remove the last 6 MD11s from service some time in 2014, I expect there will be a (small?) group of people trying to book flights on this type for one final farewell before it disappears for ever.