I bought my car used with 75k miles, with the assurance that the previous owner had gotten a new transmission installed at 50k.
I hit about 100k miles, and the transmission needs to be replaced. Checking back, it turns out the seller only had a tiny part replaced, and the transmission was by no means "new" at 50k.
Alas, the tranny died, we spent 1K+ repairingit, and then the car gets totalled by a truck less than a year later.
The car ('95 Grand Am) seemed to have things go wrong with it every other week, and while I do miss it, I am wondering how much more money I would have poured into it, if I still were driving it.
Right now, I am walking, using public transportation, and getting rides from friends/family. Fun, fun... not.