Re: ipad as instrumentation...
The Ipad is great for email and web surfing. It would be OK as a 2nd backup to a dedicated chartplotter for navigation (I wouldn't want it to be my only backup). I'll occasionally use it for planning purposes just sitting in the cockpit at anchor (using Navtonics charts) but is not going to take the place of the chartplotter with the radar overlay or the Garmin 478 GPSMap backup which can get wet, can be dropped hard and can be seen in the brightest sunlight.
I have 600+ waypoints and 50-60 routes for the Maine coast, Naraganset Bay and the Chesapeake that I can easily update and keep consistent between three different Garmin units. I would not mind being able to upload the waypoints and routes to the Navionics app I have on the IPhone and IPad. That would make the Ipad a little viable as a backup. There is no way I'm re-entering those.