Pharos GPS Receiver?

Has anyone had any luck interfacing an Arduino with a Pharos GPS-500 or GPS-300 gps receiver? I have one that is no longer being actively used with my PC, and thought I might have some fun with it with the Arduino. It has a USB interface that is easily exposed, but also has a 6 pin serial connection (power, tx, rx, and 3 grounds).

Any help would be appreciated.