I installed the latest iPhone update, which was released just a few hours ago. The first thing I tested out was the Triangularization technique for the iPhone to figure out your location and then plot it on Google Maps, within your iPhone.
This is a video of the first time I tried it:
Measuring from one side of the circle to the next, is about 1 mile long. Now, the pin, which represents my real location, is probably a few hundred off the center of the circle. But at the same time, I have horrible reception in my office with AT&T.
I tried it a second time and the pin was smack in the middle of the circle, which is what you want to see.
I know this feature will be useful when I am out and about and not in my car (i.e. without a GPS).
Update: I ran this at home and the radius was maybe 300 feet and the center of the circle was dead on!