I had a GuitarPort for a while and from what I understand, the PodXT is just a Pod and a GuitarPort in one. To record, make sure your PodXT is the default recordig device in your Sound Device control ...
You might know this already but I just found out - Gearbox software now supports Mac OS X, replacing the GuitarPort software that didn't. I spent a happy hour last night making noises like Angus Young ...