There have been over 50,000 downloads here of my maps that were made that way.

If you want anything beyond a generic Garmin map that looks like a refugee from the 1990's, you will need to learn how to create custom types however, and Globalmapper doesn't do that.
Of course, cgpsmapper was discontinued long ago and globalmapper can create many features that are not supported at all by the Garmin .img format. You might also just reflect a bit on the current state of Garmin and .img files before making such a big investment. Garmin no longer makes maps that can be installed directly into Basecamp/Mapsource. They used to offer these on DVD but discontinued that option a number of years ago. Now they only sell maps on pre-loaded SD cards or downloads. With the download option, you must connect your GPS to your computer and the map files are copied directly to it, you don't get anything to install directly on your computer.
Basecamp is EOL and Garmin just did one bug-fix to address an issue with registry-based maps on Windows and provide 64-bit compatibility on Macintosh. Garmin is clearly going in a different direction and Basecamp will not follow. But I'm sure they will have to support the current version for awhile, since it's needed for their legacy devices.
Anyway, it's pretty straightforward to export .mp files from Globalmapper and compile them with cgpsmapper. But - just my personal opinion - it's a dead end without much of a future. I recently decided to stop making maps for Garmin devices and will remove them all from my own website this summer. I will continue to offer my maps as part of my free web app, where I control everything myself.
But Globalmapper is great, I use it every day. I recently got rid of my Windows PC and replaced it with a Windows 10 virtual machine on my Mac. I assumed I'd need to upgrade to the new version of Globalmapper, since mine is almost 10 years old. Downloaded the free trial of the new version and it worked fine, but a number of things changed which I found awkward. I was then surprised that my old version worked just fine on Windows 10, so I decided to just stick with that and save the cost of upgrading.