We find this plugin really useful though we are not using the maps just now we are just using the geotagging of posts and then generating KML out of them.
I have come across a bug in that you overwrite the geo_ properties if you do a quick edit on a post. This is a bad thing!
I have fixed it in our version by adding
<input type="hidden" name="geotag_submit_flag" value="true"/>
to the form and
if( !isset($_POST['geotag_submit_flag'])) return;
to the savePostHook function
I note there has been no activity on this plugin for nearly a year. Are you still maintaining it? Would be good if you could add my changes. Anyone using the plugin at the moment should be very aware they can lose all their geo coding if they aren't careful.