My two cents: For nearly 20 years, Spaceship Earth was unadorned with any type of identification and, I dare say, none was needed--everyone knew that it was the quintessential symbol of EPCOT. Then in late 1998 or early 1999, up went the structure wrapping around the ball and reading, "2000," in preparation for Disney's millenial celebration. I thought, "Well, okay, if you really need to draw attention to the coming Y2K thing, that's fine." But after all the celebrating, the sign was changed to be what it is now.
In truth, I really don't care one way or the other, but I do have a preference: take it down, for two reasons: first, if you're looking at it, you already know where you are, so the sign is necessary. Second, Mickey's arm and hand should not be there: EPCOT was Walt Disney's dream, independent, I think, of Mickey and the world Walt created around him. That ball, unadorned, reminds all of us, as it should, of the genius and vision of the man whose life was far too short, and who gave us so much of what we love and enjoy.