When sailing last weekend in Fort Myers Beach I was able to test the full spectrum of Nav programs available for the iPhone. The only program I don't have is Active Captain as they haven't ported it to the iPhone yet. I was able to compare iNavX with NOAA Raster Charts, iNavX version 2 with Navionics Vector Charts, Navimatics Marine Maps (Now Charts and Tides), and Fly to Maps Water Map Navigator. By far the best chart data available was the Navionics Vector Data.
As this product hasn't been released and Navionics is handleing the PR side of things I can't show you a full screen shot, but here is the chart portion of the screen shot. The raster chart above was usable, but due to the low scale of the Raster, the free chart was not great for navigating the narrow channel (not that it really mattered as we still bumped a sand bar heading out due to the unusually low tide even though we were dead smack in the middle of the channel). My understanding of the plans for iNavX are that when version 2 comes out (free upgrade) Navionics will have a method to purchase and download their Vector charts (in addition to the free NOAA Raster charts). No word yet on regional packaging or pricing, but if I lived up this inlet, I would spend the money for the Navionics Vector chart as it fills in nicely for the less than stellar Raster of the region.
I unfortunately forgot to load the correct region of the Navimatics charts, an inherent flaw in a system with separate programs for different regions. That said, you can load more than one region at a time and the icon shows the active chart region. Below is what the Navimatics chart of the region looks like.
Certainly workable, but not really as good as the NOAA raster let alone the Navionics Vector. It doesn't show all the Nav Aids that line the channel, just the larger Piles at the entrance. It does show the location of the channel with a different water color, but without the smaller posts shown, it would be harder to follow.
Fly To Map's product uses the free NOAA Vector charts (S57 format). Unfortunately, there are still ~30% of the raster charts that have not been converted yet. Also, they aren't the prettiest things in the world by any means. Clearly this is a region where the detailed charts haven't been converted to Vector format yet making the software completely un-usable in this situation. Sure it only costs $10, but if you lived or sailed in Fort Myers it wouldn't be worth 10 cents.
Overall, I am very excited about the partnership of Navionics and iNavX. The iNavX software is by far the most powerful, with the new features of waypoint and track import/export just adding to the functionality. They also keep developing with promises of eventual Grib weather overlays and several other features on top of the added support for Navionics Vector charts. The Vectors are sure to be somewhat costly, but hopefully they will be priced fairly and reasonably or at least in a way that you can pick and choose the charts you want to buy to fill in areas where the rasters aren't that great, or for international use.