I think that the new GPS plotters are, for the most part, great but unnecessary toys for we coastal cruisers. Since what we mostly do is what is known as "conning", i.e. navigating mosty by sight through recognition of landmarks and navaids, the GPS with its maps are a convenience, with the additional information such as distance to go, time to destination etc. somewhat useful as well.
Even with the plotter on, I still prefer to refer to real charts, the picture is bigger, and I can view it from anywhere on the boat in most any conditions.
But, and there is a but, should you find yourself in heavy fog, then the GPS plotter can be a lifesaver. If you are fortunate enough to be able to combine that with radar, these conditions are much more manageable.
We use our GPS MAP76 all the time, I like the data it presents, but the charts are out too. On last year's trip out to the West Coast, we were well pleased to have the plotter and radar when we ran into fog, and safely navigated 90 plus miles in a day without seeing land (or traffic) till we arrived at the channel entrance.
Unfortunately we have begun to notice that there are people relying strictly on these new gadgets - forsaking real charts and tide books - and find that trend somewhat alarming. Usually newbies, it may be somewhat academic for them - if the batteries died it's unlikely they would be able to make good use of the charts even if they had them. This is another example of technology encouraging a lack of thorough preparation.