Last night, I added HTML5 Geolocation to my 0 click weather site to provide an alternative to using the GeoIP database.
Chrome and Firefox give a location within 3-5 seconds but seem to just be using GeoIP data from Google's servers. They (and GeoIP) give my location as a town 10 miles away from me.
Safari 5 on Mac OS X is basically unusable. 95% of the time it can't return a location within 10 seconds which is already way too long for a webapp. When it does work, it gives my location within a 1 block radius which is wonderful. It appears to be doing a long 2 way exchange of wifi data to Apple; probably building upon the location service they use for the iPod Touch/wifi iPad.
What are your experiences? Do you think accurate location-based services will stay mobile only? Or will laptop/computer vendors eventually add GPS/A-GPS units?