Well, I plan to use this feature mostly to find things when I'm not home, so even knowing where I am down to a few miles is good. As many people have said, this isn't - and was never advertised as - gps. But the next time you are 30 minutes from home and need an ATM or a restaurant, it ought to come in handy.
When I first tried it at home it gave me a location about 2 miles away. Tried it again a few minutes later and put me in the neighborhood... maybe a block away. I guess depending on what towers it's able to connect to it could give you different results each time.