I've had my G76 for 5 yrs and love it. I have the charts which cost me about $100 for the Great Lakes unlock. I use the desktop software extensively for planning.
That said, I've also used it in several areas I don't have the charts for and found the base map very good. For example, I spent a month in the Fl Keys and virtually every buoy and light was right where the base map said it was. Also had the same experience in Alaska and the Caribbean. I've also used it for land travel from coast to coast. All the major highways are shown in the basemap.
You should always have your paper charts anyway so I suggest you use the unit without the MapSource charts to see how you like it, then maybe spring for the MapSource charts later.
More on my personal experience with the G76 is at this link:
http://h260.com/gps/gps1.html
Mine was $300 after coupons, plus the $99 for the one chart area I downloaded to the unit. However, you can get the whole world's Garmin charts on the internet with an unlock code. That gets them onto your computer and into MapSource, but you can't put 'em on your handheld. There are so many other charting programs and geocache to use so this "free" Garmin charts on MapSource isn't nearly as "great" as I thought it would be, unless you really like and use the MapSource program a lot. Ya still gotta hand over the $99 for each unlock code to get it onto your handheld. I love our unit, easy to use (a first in ease-of-use for Garmin compared to the GPS 72 that preceded it based on our experience). We use rechargeable batteries. We have a simple, inexpensive white plastic holder on our binnacle for it, works great.
