I haven't pulled the trigger yet on any IPad nav apps. I have the primary Lowrance MFD at the helm for radar overlay, etc., the netbook at the nav desk running Coastal Explorer for plotting and planning and interfaced with AIS, and as backup a battery-operated Garmin GPSMAP 478. I think you can't beat the drag-drop nav planning capability of the CE on the netbook, and the other devices are weatherproof and sunlight-readable so I don't see a place for the iPad in the cockpit.

However, it's great for quick lookups and functions like tides/weather, anchor alarm apps etc. seem like a natural.

Yesterday we took out some guests for a 4th of July sail and it was great to be able to check (online doppler radar) the status of the local t-storm cells in the area. We went out right after one passed, and came back in before the next one (which turned out to be pretty intense, with nickel-sized hail).