Recently, I acquired a Magellan Meridian Platinum GPSr on eBay and have have spent some time figuring it out. So far, I have had no luck using the serial data cable for firmware updates or transferring waypoints. However, since the unit has a SD card (hidden behind the batteries, UNGH!!), it is still possible to work without the cable.
I have been loading waypoints into my GPSr using GSAk and selecting the 'Magellan Explorist SD Card'and when asked for "required format", I select "Magellan Protocol (SD Card)". Make sure the box for "Use Defaults" is not checked. Withe the box checked my GPSr could not read the file.
I know it's probably ten year old technology,its not paperless, but it works, and it has a tri-axle compass to boot
-Ross-