I would use "plush" to describe the ride, not the bike. And I wouldn't consider riding position to have anything to do with it; it's only that they don't put an aggressive seating position on a bike that's going to flex all over the place, because no one would want a bike like that. Someone comfort-oriented will want a plush ride and a relaxed seating position; someone performance-oriented will want a compliant ride and an aerodynamic seating position (and if they can't afford compliant, they'll take stiff over plush because it's more controllable and efficient).
Frame materials and geometry definitely have an effect, but one could also make the ride more plush by letting some air out of the tires, for instance, or putting on a sprung saddle or seatpost; and if you have adjustable suspension, by dialing in less damping on both ends, and possibly less preload as well.
You know when you test drive a car, if you buy it and bring it home, you find that the tires are like 5# under spec. The dealers do that to make the ride more plush, on the theory that most people value comfort over handling.
Last edited by OakLeaf; 07-12-2010 at 01:43 PM.
Speed comes from what you put behind you. - Judi Ketteler