The GPS was one of the main reasons that sold the iphone to me. I was thinking of buying a cheap Garmin to help when I setup my Goto mount in different locations. The iphone worked out much cheaper, and it has the possibility of running astronomy software at the same time.
Heres another link saying the GPS radio is accurate to within a few meters.
http://gpsobsessed.com/gpsdevices/ap...-not-broadcom/