The distance query works well, but I wanted to get the visitor's location from their IP address. Instead of writing a views_query_alter or something, I thought it would be nice to have this functionality within location itself. So, I modified the filter handler for proximity, and got it to support the geoip api module with a checkbox. A patch is attached - no simpletests yet but I hope it's useful anyhow.
The only thing that I wanted to get working but didn't was a way to expose the zipcode filter but still have the map come up with the user's location by default.
Oh, also there's some stuff you have to do to make the City-level database work with geoip module - described at http://drupal.org/node/813228#comment-3057436
PASSED: [[SimpleTest]]: [MySQL] 425 pass(es). View
FAILED: [[SimpleTest]]: [MySQL] Unable to apply patch 820116-location-3.1-geoip-views.patch. Unable to apply patch. See the log in the details link for more information. View
FAILED: [[SimpleTest]]: [MySQL] Unable to apply patch location_geoip_origin.patch. Unable to apply patch. See the log in the details link for more information. View
FAILED: [[SimpleTest]]: [MySQL] Invalid patch format in location_geoip_support.patch. View