Someone posted this on droid-life, it worked for me
Via adb:
adb kill-server
adb root
adb remount
adb shell rm /system/app/Maps.apk (then, back out of adb shell)
adb uninstall com.google.android.apps.maps
reboot
This procedure worked for me. A lot simpler than editing the packages.xml which can really screw you if not done right.