I've done a bit more exploring of the V2 update but to be honest kept on wondering if it was me or the software that wasn't quite right. In the end checked out their help pages (which you can find here) and decided it wasn't me.
What I was trying to do was set the waypoints at specific lat/long points, or move existing ones set to new locations, and was not successful.
But there are definite plus points for this release, like the new tide graphics that show direction and strength:
While the tide prediction seems to have lost the implausible discontinuities of previous versions the feature to highlight areas with insufficient depth seems to have its own bugs. In the pic below there are all sorts of dangerous banks outside Felixstowe, and Navionics seem to truncate them.
I did try and show off the "Track" option which shows a wiggly line of where you've been (ok, if you steer brilliantly maybe you'd get a straight line). I did this on the train to work (check out the times of the screenshots) and it was a dismal failure.
There are two problems:
1) Was very rarely able to get GPS lock in the train carriage
2) The iPhone kept switching into standby to save power
So what? you are probably thinking. Well if you use the GPS a lot and stop the going into standby then the iPhone battery will drain like there is no tomorrow. So the only way of really doing the track is to be plugged into a power, such as by the nav station, which of course would be useful place to see it.
But of course the nav station is below deck, and so there would be some attenuation of the GPS signal, maybe not as much as in a train but certainly some.
Hence what you want is outdoor electrics, which you don't often do on a sail boat but might on some form of gin palace.
Together with the inability of the depth colour feature to take account of tides makes me wonder if the target market is motor yachts in the Med.
Co-incidently Navionics is an Italian company!
Note: newer Navionics iPhone post here and previous post here