I have Navigon USA and Canada, paid version (Navigon is owned by Garmin) on my tablet which is wifi, no 3G and it works offline once the app and maps have been downloaded. Well worth the $40 I paid for it and cheaper (more convenient) than getting another device (some would say I have too many already

) GPS on my Galaxy Tab works extremely well. My daughter took the TomTom I had to use in her car but I prefer using the Tab anyways because of the bigger screen...
I can't image going back to Google maps or any other static map to find my way around!