when we tore a sail, and didn't have enough fuel to motor on to Isla Mujeres. The big Garmin chartplotter had no chip of the north coast of the Yucatan, so the Iphone got us in, right to the jetties.

Got the sail repaired, refueled, and incidentally, spent a quite pleasant week in Progreso.

Personally I prefer I Navx to Navionics. I've used the app from here (Texas coast) around to Annapolis, with quite good results. But as I said to Tom just above, my eyes are getting to where the IPhone screen is , shall we say, small?