general:
i've heard from other users that Safari works well. however, it's been my experience that Firefox is the Zooomr browser-of-choice.

Geotags:
- search doesn't work. as you've discovered, you have to pan & zoom to locate.
- i can't help with refining by tags. i know it can be buggy when making sets but i haven't used it in geotagging. when i geotag, i do each image individually from each photo's host page.
- other users preset geotags before uploading. i think they use juploader or picasa.

you can geotag with Juploader? did not know that. Will check it out...

I geotagged a couple of photos today using FireFox on XP. Worked better than I expected.

I'm using Safari on a Mac, and Geotagging is hit or miss. Search does not work (I get that same error), so I have to zoom in manually.

Once I'm there, sometimes I can tag photos, sometimes I can't. Sometimes my photos don't show up in the untagged photo window when I select a location to tag, and refining by tags doesn't work. I usually experience the same problems in Firefox.

Best way is to geotag your photos before uploading them.

I use Geosetter, does the job and is nice and easy to use.

@rafamoroni: Thanks a bunch for pointing us to Geosetter (Windows only). At first glance/testing this looks great.

(Since geotagging with Picasa/Google Earth for me is buggy for whatever reason, I was looking for an alternative but wasn't able to find one except for the slightly dated Panorado Flyer which utilizes Google Earth as well. Geosetter eats up way less RAM than Google Earth.)