I have the D90 and have used the Nikon GPS unit for the last year. I can't say it's the best as it's the only one I've used. I use it with Aperture 3 and Google Maps. I used it on a a whale watching cruse and recorded the GPS locations for over 900 shots over three hours without a miss. On that same trip I got over 4k shots most all of them with GPS data. This one uses the camera battery for its power. This does drain the battery a little faster but I did not find this to be a problem or even inconvenient. On the whale watching cruse I used one battery and still had a 50% charge on the second one after we docked.