And the continuing saga continues.
Had the car inspected by my mechanics today. Rear differential seals are ever-so-slightly weeping (recommendation, clean it, flush it, check it again in 5,000 miles, but it's probably nothing to worry about). Clutch is "stiff" and they say it feels as though it's nearing its end of life even though it's not slipping yet. Needs brakes immediately, both pads and rotors.
Noticed the local BMW dealer listed in the Carfax report, so I called their service desk to see if anyone remembered the car. The service guys did and were able to pull up complete maintenance records for the car. Apparently the car was sold new by the local dealership and has been serviced there ever since. The owner never missed any of the recommended services and, according to the service manager, was usually early for its maintenance requirements. Most recent brake job was the fronts, 30,000 miles ago, with a 4-wheel brake job about 60,000 miles ago, which basically confirms the analysis by my mechanic that the car needs brakes essentially immediately. Cam position sensors (the only common electronics issue with the '01 M5) were replaced at 30,000 miles with the revised design, so the VANOS system should be good.
There was one bombshell though. The car is on its original clutch. While it's possible that the owner had the clutch done elsewhere, that is extremely unlikely since every other service (including mundane things like tires and the battery) was done by the dealership.
So, basically, what I am looking at is a perfect 1-owner M5 with a complete service history that "only" needs brakes (now), and a clutch (within ~10,000 miles). This is $5,000 worth of work, but it's also routine maintenance that isn't, or shouldn't be, surprising.
ZV