I ve been using Garmin blue chart now for probably two years, both on my iphone and ipad after using inavX and a couple of others for a while.
Works great, includes active captain data and has very accurate bahamas charts.
On my iPad it is my primary nav source over the furuno nav net.
I use it quite a bit on my iPhone in the tender, including to check out depths in shallow spots here in the Exumas. Has a track recording feature that comes in handy, once I have the track recorded on th phone I can follow it in the boat and record it both on the furuno and my iPad for future use.
The down side is that in an exposed cockpit, you can't leave the iPad (or iPhone) running in the sun or it will shut down after a while.