I agree about Navionics missing ActiveCaptain. Other than that it's really cool. I also have Skipper for AC data, but that program is no longer supported as of next year. I can use the free version of Garmin for AC data also, even if I don't pay for the detailed charts, or get another app that supports AC.
I like that Navionics is only $10 for the iPhone. I purchased the Nav module, autorouting and Advanced map options for a few bucks. It's per year but that's ridiculously cheap. I don't like the $49 per year iPad price, but I have other nav programs for larger screens (including my Surface Pro running ActiveCaptain and AIS overlay within Coastal Explorer, and AIS overlay on the 7" B&G CP at the helm, using Navionics a chart chip. The Surface Pro screen and processing speed is incredibly better compared with my iPad Air 2 with retina screen, though I haven't used an iPad Pro yet.)
I like the Navionics autorouting feature because it's so quick and easy. I don't trust it enough not to check it at higher zoom levels, but (given that the program has a setup screen for your draft and air draft) I have yet to see it mess up. There's nothing better than autoroute when we're discussing destination options and the Admiral says "How much time will it take to sail from X to Y?" I can say "assuming an average speed of 6 knots, it will be ---".
I like that (for Navionics charts) the depths shown are adjusted for tide level in real-time, now, whenever that is.
I like that they allow you to easily switch between Navionics, NOAA, and SonarChart (crowd sourced from participating user's depth sounders). Remember when I recently reported ~4 feet outside Tashmoo entrance? SonarChart shows 5 feet, but Navionics and Government charts show 6 feet.
I like the weather overlays -- they are from the best sources on the Internet and they're well displayed for boaters showing tide/wind along with other weather info, but they display it formatted better for sailors so all the relevant info is there in one place.
I like that tide stations are clearly depicted on-chart and detail graphic cycle predictions are easy to access;
I like that current direction arrows are shown in real-time onscreen (on Navionics charts) and the size of the arrow represents the speed, and I like that you can change the time on-screen to show animations of what happens to those currents at different times/dates.