Steve, I've been using synthetic oil since 1979. A friend I worked with brought in an article about how some "dirt track" racers were using it in their race car engines, and differentials, and were experiencing some good results. I believe the company was called "Olmo" or something like that. It also spoke about how some trucking companies were using it and extending their oil change intervals to 24k miles and saving a lot of money.
There was only one auto store in Akron that sold it, and it was less than 1/2 the price of Mobil1 at the time, so I started using it in my (then new) 280ZX. I still changed it every 3 or 4k miles though.
About a year later they stopped selling it in qt. cans, but only in 55 gal. drums, so I had to switch to Mobil1.
One thing in that article that I found interesting was it said not to use their oil in a "new" motor until it was adequately broken in. I wrote to them, and told them my 280ZX had 4,500 miles at the time, and when did they feel it was suffentially "broken in"? They responded by telling me not to use their oil until I had over 7,000 miles on the engine. That impressed me, since they didn't tell me to just run out and purchase their oil as soon as possible. It's funny how things have changed over time, and the engineers have determined that it's OK to use it right from the start now.
Coincidently, at just over 7,000 miles (and before I started using synthetic oil) my car miraculously seemed to "loosen up" and start performing better. I decided that it was just my imagination, and the power of suggestion. But I did notice a change for the better in fuel mileage, without changing my driving habits one bit.