I use the AGP-AX 500 with FCPX and all ok.
You can import from camera or to do the "ingest" in FCP X or use PC connection with firewire (400to400 or 400to800 in my case) to conect the camera to Mac Pro for import the footage.
In the Panasonic website you can donwload several drivers to manage and mount the p2 cards in your system. You will check all clips and import in the FCPX import window meanwhile the footage is imported in the background you can use.
I found one issue with long clips only. More than 30 minutes clips don´t import properly and I need use the ingest camera option in the FCPX.