Nav Planner is simply awesome. Not only can you view your electronic charts and waypoints, you can manipulate data as well.
You can change names and icons for your waypoints much faster than on your machine. You can create new waypoints or delete old ones. I use this to plan my next day on the water from the comfort of my home or hotel room.
A nice feature is the measure feature. You can find the distance between two waypoints in the click of a mouse. Great planning tool for tournament day time management.
The other nice thing is that you can convert to and from any other brand of GPS that supports Navionics charts. I transfer to and from Humminbird/Lowrance/etc all the time.
It is a great tool and one I am glad I have learned to use.