Great thread, just had a couple of days use of the GPZ. It has the edge on the 5000, depth, smoothness and size wise, the wireless and no battery cable a godsend. But to sum it up IMO, if you own a gold detector whether VLF or PI and have not found gold the GPZ will not improve your lot. To be brutal if that is so, it is not the detector you should change. Takes perseverance and a ton of foot work and also very importantly faith in your detector.
On the GPZ`s inbuilt GPS, it is hampered by Minelabs software. Having used Oziexplorer (OZI) (another OZ product), for me that is the way Minelab should go. Allow waypoints and tracks to be imported into OZI PC version now, with a future touch screen that will allow OZI to be installed on the GPZ, like the OZI android app for smart phones. Geological maps in digital form, showing those fault lines, intersections etc are as important as the detector.