The good stuff.

I downloaded Navionics onto this iphone5c simply as a redundant CP onboard. That was 'free' in that I already have the phone, which is always on me. We have an onboard CP that's reliable, we're used to, that is our main source of navigation for our coastal sailing in NE. Secondary is an ipad with Garmin Bluecharts. All different receivers, power sources, chartware. Great to have this new redundancy from devices we have at home, for a fraction of the cost of our ancient onboard CP. My charging needs compared to a laptop have been cut.

Handy to pull a device out of your pocket and check/double check speed and bearings. A touch screen is a much handier tool than the onboard CP button tools(but I won't use those as much with touch screens nearby).

I like the Navionics 'beam' that gives me a visual bearing as I sail. Sailing higher now? Will you clear that point(another opinion in your hand)?. I don't know much about Navionics app yet but it's simple to use right off the bat.

I like this new track recording stuff. It's neat to analyse the details of a sail into a harbor or constricted area. The feedback of time and speed is interesting to compare with your other sources and senses aboard.

The downsides. Running a track-which meant the CP was on constantly, I killed the phones battery in about 5 hours.

If I fiddle with this long enough, it will go overboard. Not many pockets that can be trusted on a sailboat. I need a handy spot to keep it inside the companionway, easy to reach but out of my pocket most of the time.