Just hit 223,000 miles with no major issues. Radiator replaced by shop after being damaged by mechanic, but other than that, all original parts. Regularly serviced. As a valet, I've had plenty of competition to compare my car to, and have found the 1st generation Explorers to be one of the most agile and reliable vehicles around. I've parked a couple of Explorers with over 500,000 miles with original engine and transmission, and the owners still ... and mine feels like it could go as long, too! Exterior in good shape, some dings and dents but paint holds up well ... interior in even better shape, looks ten years younger than it is. Gas mileage is lackluster, but hey, no vehicle is perfect.
Engine is bulletproof... I've never heard of one of these 4.0L giving anyone any grief. I'm sure it's happened, but it must be rare. Interior is much better quality than some Fords five and ten years newer. 4WD still works, handling is superb for an SUV. Overall quality and reliability is amazing.
I've driven the newer Explorers quite a bit, and Ford has definitely ironed out some of the little quirks, but the newer vehicles are much bigger and have lost a decent amount of agility, offsetting the space gain. Wish my car had airbags, a better stereo, better gas mileage ... still a great car!