Yes. I've disabled or remapped the PTT, GPS, MEdia Net, and Camera keys. In case you haven't already seen MagicKey's instructions (not mine)...
For the GPS key - once you get MagicKey installed, start the app (it'll be in the Games & Apps menu). Click the right joystick button to move to the Keymap List page. Click the center button to select Default Keymap. Click again to Add Key Pair. When the screen comes up with Original Key and Maps To, press the green Send button on your phone and then press the GPS button (or just enter 226). Arrow down to the Maps To field and either hit the green send button and the down arrow or enter 17 to map the GPS button to the down arrow. Press the left select (OK) then the right select (Back) and the right select again (Exit).
Through a similar process you can map the PTT button (key code 181) to 0 to disable it, or map it to any other key.
To see a full list of possible codes, press the center key in either the Original Key or Maps To fields.
That's it - you're done.
One caveat about MagicKey is that it will not start automatically if you reboot the phone. Although there is an option to "start on boot," it does not work on this phone. That's where an app called PowerBoot comes in. It will let you autostart the KeyMapDaemon that is needed for MagicKey to start working on boot.