You need USBModem, in my experience. I am working just fine with the latest (1.07) of the Palm software and Diablo.

Google Maps worked great with my Holux GPS, as soon as I upgraded from the ancient version of Google Maps that was on the Centro.

Unfortunately, the Centro is working well enough in general that I am taking my N800 with me less often. For example, I am about to go pick someone up at LAX and I probably won't bring it, just the phone.