dgs, I've used a Solmeta GeoTagger Pro for about 18 months. It is a very nice GPS accessory. It syncs up so quickly that it makes me think why can't other GPS units work this well. I leave it and the camera on all day and it is always ready and accurate. From a "cold" start, it is always sync'd up in 30 seconds.
Another advantage with this unit is the bearing data which shows which direction you are facing when the photo was taken. Very useful for identifying distant mountains in some of my Shenandoah and Great Smokey Mountain National Parks shots. Combined with focal length in View NX2, the indicator shows not only the direction, but the angle of view, also. Quite handy.