Re: iPhone4 and iPad2 w/o 3G
We have the Ipad II Cellular model but don't need the cell coverage for INavx as long as you download the charts before you depart. I have it loaded on my phone as well for redundancy and it's been awfully handy to pull it out when we're sitting away from the boat when we have a quick question about a route, etc. Their customer service is excellent as well. We also have Aye Tide to compliment INavx and Boating Suite for boat log/maintenance info. Love INavx and it's really intuitive and powerful. In our area (Puget Sound), you can activate the AIS and see (but not transmit...) other boats nearby, including the large behomoths!
Yes, we have all the paper charts, too...