I, too used Carfax when I was looking for my '87 244. When I ended up buying one, I knew the fellow, and he was the original owner. Before i looked at it, he told me the mileage (over 250K), but when I looked at it, I was puzzled to see only 159K. Turns out it had a broken odometer at 246K (w/repair bills to back it up). Those trusty instrumnent clusters are easy to swap, especially for dishonest purposes. (saw a '90 the other day with 12K...) Carfax reported the correct changes in titles and such for that car. So that was good.

However, I checked my car I was going to sell. It was a 3-owner car, the last two being my father and myself. For this one, it only showed the transfer between the dealer and the first owner, and my father and myself. So, Carfax can be a little sketchy. Also, on both cars, there should have been more records-- the '87 was in a smog-checking state for at least its first 8-9 years, and it only reported a few non-concurrent checks.

There. That's my two pennies.