Francis Everitt, the leader of the Gravity Probe B, described below, was interviewed on Science Friday. He talks about how it took years to model the errors that ruined the precision of the gyroscopes, and that they only found a way to confirm relativity after subtracting out those modeled errors.
He also makes an analogy to a ball submerged in honey, and to the discredited Aether drag hypothesis. Supposedly relativity eliminated the aether, but as he acknowledges, that is not really true. The motion of the Earth has a very slight effect in dragging the structure of spacetime along with it. In a sense, the Gravity Probe B is the modern aether drag experiment.