Navionics on the Ipad does not have the chart detail of a full chartplotter. Also, I know everyone say that Navionics has all these cool features like real time weather and tides, etc, but I haven't figured out how to find all that on the program. All I have accessed so far is the basic maps.
For me, this is not a replacement to a chartplotter. I use it to plan my route, or study my course, before I get on the boat. That way when I'm cruising I'm already familiar with the area and any possible obstructions, vs. seeing it for the first time on a chartplotter at 70 mph.