I have to say, I had a real problem with Navionics for my Android. I bought East Coast US from them for $14 early last season. At some point, they bundled EUS and Great Lakes and sold them for $9. When they did that, they pulled EUS from the market. When I had to reinstall software on my phone, I could not reinstall the version I had bought.
I insisted they upgrade me to the current product seeing as how I had already paid more than that. They refused and eventually, after much vocal complaining, they emailed my the app but promised it would not get any updates.
I am still unsatisfied with their customer service.