I purchased a Magellan Meridian Platinum on the 4th, along with MapSend topo US and a 32 meg SD card. When I got home and unpacked everything, I realized that the PC cable provided by Magellan was a 9 pin DB serial connector. My iMac only has USB and no serial ports. The next day, I went to Fry's and found a USB PDA/SERIAL Adapter by IOGear (model GUC232A) for $39. It took a bit of work to get Virtual PC to find the Driver on the CD provided by IOGear, but once I did, all I had to do was go into MapSend and have it AutoConfigure the GPS port. I found that the max baud rate I could get was 19200 (I'm not sure if MapSend is limiting that, or the IOGear driver). Now everything is working fine and didn't cost me too much in additional hardware.
--Marky