My Model S P85 (Vin x6817, I believe) has over 75000 miles on it. We did get a new DU because of the wearing out of a gear component and that, along with an initial problem with the handles, has been the only major problem the car has had.
The Tesla motor is basically a 100+ year old design and works well, so the only possible problem is the execution of that design. As another poster said, the wiring looks to be very cleanly and professionally done. Watching a recent behind the scenes video showing the motor being built at the plant, it seems to be quite well built - but as another poster said, there are just too many variables for anyone not directly testing the unit to tell.
FWIW, I'm an electrical engineer and physicist and have built similar (not nearly as powerful or professional) motors in the past.
Jason
I'm an engineer too, Electronic Engineer in my case. As far as engineering for motors goes, there isn't all that much new under the sun, however an old technology executed well or badly. Getting things from China can run the gamut from close to the best in the world to dangerously bad (mostly due to counterfeits), it all depends on how much time and effort and quality of materials the company making them wants to put into it.
One thing I have observed is Tesla packs the drive system for their cars much tighter than any other car out there. Hybrids are going to have more inside that pure EVs, but the Leaf, Bolt, and i3 all seem to be much busier under the "hood" than Teslas, though the Model S and X are much larger cars than any other BEV, they also have much more output from the motors than other BEVs too. One thing I haven't been able to determine for sure is whether the better use of space is an illusion due to being a bigger car, Tesla just packaged the whole thing better than anyone else, or Tesla is getting a lot more out of smaller motors than the competition. Or some kind of mix of all three.
If Tesla is getting more out of smaller motors, there could be a long term reliability problem lurking there. Smaller parts put under more stress are just going to have shorter lives most of the time. It's one of those engineering trade offs you have to factor in.
However out in the real world, we have little hard data to look at because even though there are cars with more than 100,000 miles, virtually none of those have original drive units. Very few people have had catastrophic drive unit failures, most replacements have been due to abnormal noises (which might lead to dead on the road failures if it was left to continue, or it may not). Most stories of people who have been stranded had to do with some kind of electrical failure, usually battery related.
I am kind of skeptical of the urban legend nature of this story: "I heard from this guy..." There are some people who are tearing apart junked Model Ss and learning what makes it tick. wk057 here on this forum is one of them. There is a YouTube video from a guy in Germany who got the drive unit from a Mercedes with a Tesla drive train working on a bench. Though I don't know of anyone who has done a thorough analysis of the motors and published any kind of report on the quality. Until someone is willing to publish and put their name on it as well as provide the data that led to their conclusion, I'm going to take these types of stories with a grain of salt.