With regard to ContinentalEWR's initial question, I contacted United myself during the spring of 2000, having noticed the new U N I T E D font everywhere but the aircraft.
The reply, from UA's PR department, was that they are currently refining the airline's brand name. She said they're not starting with the aircraft in doing so, like other airlines have done (Delta most recently), but with the things passengers see most, like check-in counters, gate check-in desks, etc.
She added that we could expect the new identity to extend to a new aircraft livery in "one and a half to two years."
So it's just about time to see that new livery. I don't know how UA's mounting losses affect those expensive plans, but as of April 2000, that was the plan UA communicated to me. Hope this helps...