I just bought a CPO X90D. My experience was the savings made it worth it over the new 75. Also, the performance was significantly different when I bought (July) but that is not less of an issue no with the recent changes to new 75s. My vin is 6551 and its had a few minor issues which have been taken care of by Tesla. I like the fact that I essentially get the 50k new car warranty reset. My X had 20k miles on it so it will have full coverage up to 70k miles. Range was a factor for me so it was worth it to get an optioned out CPO 90 vs new 75.
I'm very happy with the car but did not like the process. There was very little communication and I went weeks without any update. I can understand having to wait for a car to be built but a CPO should be ready to go. I was not happy that I received no pictures or service history of the actual car. From the time I clicked the buy button on the website until I picked up my car was about 6 weeks. It was also used as a loaner for a period of time and had 400 miles more on it than when I clicked buy (Tesla thru in the Chademo adapter to compensate). It was a very strange feeling paying $90k for a used car that I had never seen or driven.