I do not use a Garmin GPS but like to work with different mapping software. MapSource works ok but can be frustrating. Just loaded BaseCamp and already like it more than MapSource.
Still my prime mapping is done on Delorme Topo9, just more entertainment on a snowy afternoon!

butthead

Never used MapSource. I've been using BaseCamp since June and initially found many of its features pretty amazing, mostly due to the fact that my 62st was my first gps offering a computer interface. I especially like being able to edit trails: eliminating stray trail points, splitting trails into sections, etc. However, I especially detest BaseCamp's insistence that every waypoint have a unique name, forcing my walleye marks -- all of which I would like to remain named 'W' -- to be named things like W49, W50, W126, etc.

Connect the gps with the map chip inside and BaseCamp will recognize it... showing LakeMaster's lake depths, for example. Any Garmin custom map that you can create, like a jpg of the Pagami Creek daily fire progression, can be displayed, too. Import the gpx files from the Arch Harris collection and copy a select subset to your gps for an upcoming trip. Draw your own trails and save them to the gps. Measure distances of straight lines or serpentine routes. Display elevations of trails. It's pretty good stuff for free.