Well ladies and gentlemen, Dave Doyal, the chief geodetic surveyor for the National Geodetic Survey, which defines and manages a national coordinate system, says I HAVE visited the Four Corners (as I suspected).
The long and the short of the article is that the marker is 2.5 miles off if starting from the Prime Meridian in Greenwich, England. In fact, the original mandated measurements were supposed to be based on the Washington Meridian, which runs through Washington D.C. Using the D.C. meridian, the monument is only 1,800 feet east of the true spot. When you consider the types of primitive surveying instruments/tools they used, 1,800 feet is actually quite impressive.
In any case, the measurement differences don't matter anymore - as I stated in my previous post and as Doyle confirms. "The monument controls. Where the marker is now is accepted, Doyle said. Even if it's 10 miles off, once it's adopted by the states, which it has been, the numerical errors are irrelevant. It becomes the legal definition of the Four Corners."
Whew. Good to know I haven't lived "a bit of a lie".