First off, I must say that you are very fortunate to have Casco Bay as your sailing grounds. It is not unlike our own Puget Sound, with their beautiful islands, channels, and coves, -a almost lifetime of sailing. But in the fog, these types of sailing grounds can be the most treacherous, and this is where a chartplotter shines.
Yes, I too have my paper charts and handhelds. Hell, I'm even half decent at celestial navigation (which I would recommend that everybody learn). But when the pea soup fog rolls in down a narrow channel when beating to windward, your nerves will be on edge. You'll want 'real-time', right now, information. And the last thing you'll wanna be doing is running up and down to your nav station, fixing positions. Trust me, been there, done that, -got the shirt
EDIT: Looks like JRD (fellow Puget Sounder it appears) beat me to the punch.