I've been using an Easytag for about a year now, 12 hour battery life, plugs directly in Nikons using the ten pin connector, has a 2 GB micro SD card and I'm nowhere near full. Writes standard NMEA format, fairly quick lock-on and will embed orientation if used directly with camera. Works on a single shoy mode and a continuous track mode. Will also draw on camera power if internal battery runs down. I usually just carry it in my pocket and let it make a track for where ever I am, don't need more stuff hanging off the camera to get banged around. Bad side, plugs into a "rounded" USB port to charge battery and must remove micro SD card to get track data, they provide an adapter for a standard USB port. I have found PhotoLinker a useful adjunct to PM and also GPSBabel for making Google Earth track files. For ease, I leave the cameras on GMT and can correct image time later in PM if I need to, haven't ever needed to do that though.