OK - so I finally got my data acquisition system set up and working. It's a Garmin iQue 3600 with built in GPS connected to a PakTrakr. I just tried it out on a 4 minute jaunt around the neighborhood - it seems to work. The advantage of this system is that it integrates both battery and GPS data into one file.
You can check out the data here: http://www.editgrid.com/user/jdh2550/xm2000-firstrun (editgrid is an amazing online spreadsheet - I highly recommend it).
I haven't done any pretty graphs or even looked at the data very closely. One thing to note is that the elevation data is pretty worthless - I just don't think GPSs are very good at resolving accurate elevations.
The only purpose of this run was to test the system. I plan on having it hooked up for my 12 mile commute tomorrow.