afrey--
I can't speak for your GPS, but I do note that your code appears to be printing the raw GPS position data. If you are noticing variations directly in that, be advised that GPS latitude and longitude are measured not in feet, but in degrees and minutes. Specifically, latitude is in the form ddmm.mmmm and longitude dddmm.mmmm.
The least significant digit is measuring 10000ths of a minute, which is somewhat smaller than a foot.
To test your GPS parsing, you might compare the results with my TinyGPS object.
Mikal
EDIT: Just as an experiment, I ran my GPS for an hour and it drifted +/-60 meters. It was positioned very far from any exterior window, though, so I'd expect this to improve outdoors.