If you use Firefox's geolocation support[0], you're seeing the benefits of this[1].

FWIW, I find that it is FAR more accurate than my iPhone indoors. Without the line to a satellite, my iPhone is generally wrong by a radius of a few blocks, while Firefox is generally within a few meters.[2]

[0]: http://www.mozilla.com/en-US/firefox/geolocation/

[1]: http://www.google.com/privacy-lsf.html

[2]: NOTE: This is from Los Angeles, a heavily populated area, which probably makes it easier. YMMV.