When I got my GPS (Garmin ForeRunner 201) I too was hoping to do away with all the other electronic instrumentation festooning my handlebars. Alas, there are still places where it's virtually impossible to get signal from GPS satellites (deep canyons, roads with dense tree canopies), even with the newer SIRF III chipsets, so it's not practical to dispense entirely with a humble odometer/speedometer/time-keeper.

There's various kinds of software for Mac, depending on what you wish to do. A lot of it is even free and quite good. Garmin belatedly has started supporting Macs, but only on their newer devices which have USB ports. Owners of olders devices with serial ports are out of luck, even if they use a serial-to-USB adapter to connect to their computer: the Garmin software simply doesn't recognize such connections. Try searching for "gps" on MacUpdate.com and/or VersionTracker.com for software to work with your GPS device.